The most popular computer language is Visual Basic for Windows (VB). More programs are written in VB than in any other computer language.

Using VB, you can easily create Windows programs that let the human use a mouse to click on icons, choose from menus, use dialog boxes, etc.

After inventing the first VB, Microsoft invented improved versions, called VB 2, VB 3, VB 4, VB 5, VB 6,
VB 7 (which is also called VB.Net),
VB 7.1 (also called VB.Net 2003), VB 8 (also called VB 2005), VB 9 (also called VB 2008), and VB 10 (also called VB 2010). The most traumatic change was the switch from VB 6 to VB 7: programs written for VB 6 must be rewritten to work with VB 7.

You can buy Visual Basic separately or as part of Visual Studio, which is Microsoft’s suite of programming languages. Visual Studio includes
Visual Basic, Visual C++, Visual C#, and other programming tools.

Microsoft lets you get stripped-down editions of VB (and the other Visual Studio languages) free! They’re called Express Editions. Copy them, free, from the Internet at:

To copy them quickly, you need a broadband Internet connection (such as DSL or cable).

This chapter explains VB 2010 (which is also called VB 10).

Before you read this chapter and study VB, prepare yourself! Do 2 prerequisite activities:

VB uses these commands (which resemble QBasic’s):

VB uses these functions (which resemble QBasic’s):

In VB, you never write “a long program”. Instead, you begin by drawing objects on the screen (as if you were using a graphics program). Then for each object, you write a little program (called a subroutine) that tells the computer how to manipulate the object. VB handles these objects:

Each object has properties, which you can manipulate:

Let’s have fun programming!

Copy VB to the hard disk

Here’s how to copy Visual Basic 2010 Express to your hard disk by using Windows (Vista or 7) and Internet Explorer.

Start VB

To start using VB, click the Start button then do this:

You see the Start Page window.

Create simple programs

Click “New Project” (which is near the screen’s left edge). Double-click “Windows Forms Application”.

You see an object, called the Form1 window. Double-click in that window (below “Form1”). That tells the computer you want to write a program (subroutine) about that window.

The computer starts writing the subroutine for you. The computer writes:

The line saying “Private Sub Form1_Load” is the subroutine’s header. The line saying “End Sub” is the subroutine’s footer; it marks the end of the subroutine. Between those lines, insert lines that tell the computer what to do to the object (which is the Form1 window). The lines you insert are called the subroutine’s body.

Simplest example Let’s make the Form1 window show the answer to this math problem: 4 + 2. To do that, type this line —

The computer automatically indents that line for you, so the subroutine becomes:

To run your program, press the F5 key (or click the green “4”, which is at the screen’s top center). Then you see the Form1 window again; but instead of saying “Form1”, it says the text’s answer:

When you’ve finished admiring that answer, stop the program by clicking the Form1 window’s X button. Then you see the subroutine again:

Edited example Let’s edit that subroutine, so instead of saying the answer to 4 + 2, it will say the answer to 79 + 2.

To do that, change the 4 to 79. Here’s how: click the 4’s left edge, then press the Delete key (to delete the 4), then type 79, so the subroutine looks like this:

Run that program by pressing the F5 key. Then the Form1 window shows the new answer:

When you finish admiring that, click Form1’s X button.

To make the computer subtract 3 from 7, change the text line to this:

When you run the program (by pressing the F5 key), the Form1 window will show the answer:

To make the computer do -26.3+1, change the text line to this:

The Form1 window will show the answer:

Your own examples Go ahead! Try changing the subroutine, to do different math problems instead!

Multiply To multiply, use an asterisk. So to multiply 2 by 6, type this:

The Form1 window will show:

Divide To divide, use a slash. So to divide 8 by 4, type this:

The Form1 window will show:

To divide 2 by 3, type this:

The Form1 window will show:

Congratulations You’ve written VB subroutines and created VB programs, so you’ve become a VB programmer! You can put on your résumé, “VB programmer!”

Type faster

Here are tricks that let you type faster.

You don’t need to capitalize computer words such as “Text”. The computer will capitalize them automatically, eventually. For example, if you type “text” instead of “Text”, the computer will change “text” to “Text” when you type the equal sign afterwards.

You don’t need to finish typing computer words such as “Text”. The computer will finish typing them for you, automatically, eventually, if the computer can deduce what you meant. For example, you can type “te” instead of “Text”; the computer will change “te” to “Text” when you type the equal sign afterwards.

Instead of typing computer words, you can choose them from lists. For example, instead of typing “Text”, you can do this:

You don’t need to put spaces around symbols, such as “=” and “+”. The computer will insert those spaces automatically, when you end the line (by pressing the F5 key or Enter key or down-arrow key or clicking in a different line).

Huge and tiny numbers

When dealing with huge and tiny number, be careful!

Avoid commas Do not put commas in big numbers. To write four million, do not write 4,000,000; instead, write 4000000.

Use decimals for big answers The computer sometimes has difficulty handling answers bigger than 2,000,000,000, which in modern English is called “2 billion.” To avoid difficulty, put a decimal point in any problem whose answer might be bigger than 2 billion.

For example, suppose you want the computer to multiply 3000 by 1000000. Since the answer to that problem is 3 billion, which is bigger than 2 billion, you should put a decimal point in that problem, like this:

After typing a decimal point, you must type a digit (such as 0).

Suppose you forget to insert a decimal point and say just this:

When you try to run the program (by pressing the F5 key), the computer will complain in 3 ways:

E notation If the computer’s answer is huge (at least a quadrillion, which is 1000000000000000) or tiny (less than .0001), the computer will put an E in the answer. The E means “move the decimal point”.

For example, suppose the computer says the answer to a problem is:

The E means, “move the decimal point”. The plus sign means, “towards the right”. Altogether, the E+15 means, “move the decimal point towards the right, 15 places.” So look at 1.586743 and move the decimal point towards the right, 15 places; you get 1586743000000000.

So when the computer says the answer is 1.586743E+15, the computer really means the answer is 1586743000000000, approximately. The exact answer might be 1586743000000000.2 or 1586743000000000.79 or some similar number, but the computer prints just an approximation.

Suppose your computer says the answer to a problem is:

After the E, the minus sign means, “towards the left”. So look at 9.23 and move the decimal point towards the left, 6 places. You get:

.00000923

So when the computer says the answer is 9.23E-06, the computer really means the answer is:

.00000923

You’ll see E notation rarely: the computer uses it just if an answer is huge (at least a quadrillion) or tiny (tinier than .0001). But when the computer does use E notation, remember to move the decimal point!

The highest number The highest number the computer can handle well is about 1E308, which is 1 followed by 308 zeros. If you try to go much higher, the computer will gripe, by saying “Overflow” or “Infinity” or “NaN” (which means “Not a Number”).

For example, if you say —

the screen’s bottom will say “Overflow”.

Dividing by 0 If you ask the computer to divide by 0, the computer will have difficulty.

For example, if you say —

the computer will try to divide 5 by 0, give up (because you can’t divide by 0), and say the answer is “Infinity”.

If you say —

the computer will try to divide -5 by 0, give up (because you can’t divide by 0), and say the answer is “-Infinity”.

If you say —

the computer will try to divide 0 by 0, give up (because you can’t divide by 0), get confused, and say the answer is “NaN” (which means “Not a Number”).

The tiniest decimal The tiniest decimal the computer can handle accurately is 1E-308 (which is a decimal point followed by 308 digits, 307 of which are zeros). If you try to go tinier, the computer will either say 0 or give you a rough approximation.

Order of operations

What does “2 plus 3 times 4” mean? The answer depends on whom you ask.

To a clerk, it means “start with 2 plus 3, then multiply by 4”; that makes 5 times 4, which is 20. But to a scientist, “2 plus 3 times 4” means something different: it means “2 plus three fours”, which is 2 + 4 + 4 + 4, which is 14.

Since computers were invented by scientists, computers think like scientists. If you type —

the computer will think you mean “2 plus three fours”, so it will do 2 + 4 + 4 + 4 and display this answer:

The computer will not display the clerk’s answer, which is 20. So if you’re a clerk, tough luck!

Scientists and computers follow this rule: do multiplication and division before addition and subtraction. So if you type —

the computer begins by hunting for multiplication and division. When it finds the multiplication sign between the 3 and the 4, it multiplies 3 by 4 and gets 12, like this:

So the problem becomes 2 + 12, which is 14, which the computer will display.

For another example, suppose you type:

The computer begins by doing all the multiplications and divisions. So it does 2 * 3 (which is 6) and does 72 / 9 * 5 (which is 8 * 5, which is 40), like this:

So the problem becomes 10 - 6 + 40, which is 44, which is the answer the computer will display.

Parentheses You can use parentheses the same way as in algebra. For example, if you type —

the computer will compute 5 - 2 and print:

You can put parentheses inside parentheses. If you type —

the computer will compute 10 - (5 - 2), which is 10 - 3, and will display:

Strings

Let’s make the computer fall in love. Let’s make it say, “I love you”. To do so, type this in your subroutine:

Type that carefully:

When you run the program (by pressing F5), it will make the text (at the top of Form1’s window) display:

You can change the computer’s personality. For example, if you edit the subroutine to make it become —

the computer will reply:

Notice that to make a subroutine print a message, you must put the message between quotation marks. The quotation marks make the computer copy the message without worrying about what the message means. For example, if you misspell “I love you”, and type —

the computer will still copy the message (without worrying about what it means); the computer will make Form1 say:

Type faster Instead of typing —

you can type just this:

Before the computer runs the program, the computer will automatically capitalize the first letter of “text”, put spaces around the equal sign, and put a quotation mark at the line’s end (to match the other quotation mark).

Red strings While you’re typing the subroutine,
the computer makes each string look red (and each computer word look blue).

Those colors appear just while you’re looking at the subroutine you’ve been typing. When you run the program, the program’s answers (and other results) appear black.

Jargon The word “joy” consists of 3 characters: j and o and y. Programmers say that the word “joy” is a string of 3 characters.

Strings versus numbers The computer can handle two types of expressions: strings and numbers. In your subroutine, put strings (such as “joy” and “I love you”) in quotation marks. Numbers (such as 4 + 2) do not go in quotation marks.

Combine strings You can combine strings:

The computer will combine “fat” with “her”, so the computer will display:

You can combine a string with a number:

The computer will display “The lucky number is ” then the answer to this math problem: 4 + 2. The computer will display:

When combining a string with a number, make the computer leave a space between the string and the number, by putting a space before the last quotation mark.

Combining strings or numbers (by using the symbol “&”) is called concatenating.

When typing the symbol “&” to concatenate, press the keyboard’s Space bar before and after the “&”. If you rely on the computer to put those spaces in automatically, you’ll be sorry, because the symbol “&” without spaces can have a different meaning, and the computer will occasionally guess wrong about which “&” you meant.

Accidents Suppose you accidentally put the number 2 + 2 in quotation marks, like this:

The quotation marks make the computer think “2 + 2” is a string instead of a number. Since the computer thinks “2 + 2” is a string, it copies the string without analyzing what it means; Form1 will say:

It will not say 4.

Suppose you want the computer to show the word “love” but you accidentally forget to put the string “love” in quotation marks, and type this instead:

Since you forgot the quotation marks, the computer is confused. Whenever the computer is confused, it either gripes at you or says zero. In this particular example, when you indicate you finished typing the line, the computer will gripe at you by making the screen’s bottom say:

Display a quotation mark The symbol for inches is ". Let’s make Form1 say:

This Text command does not work:

When the computer sees the quotation mark after 2, it mistakenly thinks that quotation mark is paired with the quotation mark before “The”, then gets totally confused.

Here’s the correct way to write that line:

The symbol "" means: display a quotation mark. That Text line makes Form1 display:

Here’s the rule: to display a quotation mark ("), put the symbol "" in your Text statement.

Let’s make the computer display this sentence:

To display the quotation mark before “Hamlet”, you must type "". To display the quotation mark after “Hamlet”, you must type "". So type this:

Color

Normally, the Form1 window’s middle is a big blank area that’s nearly white (very light gray). To make it red instead, put this line in your subroutine:

For example, to make the window’s title say “I love you” and make the window’s background color be red, put both of these lines in your subroutine —

so the whole subroutine looks like this:

The computer understands these color names:

It understands many others, too: altogether, it knows the names of 141 colors. You’ll see the complete list when you’ve typed:

(Use the list’s up-arrow & down-arrow.)

Don’t put spaces in the middle of a color name: type “DeepSkyBlue”, not “Deep Sky Blue”.

Beep

To make the computer beep (ring its bell), put this line in your subroutine:

Multi-statement line

In your subroutine, a line can include many statements separated by colons, like this:

That line means the same thing as:

Maximize

To maximize the Form1 window (so it consumes the whole screen), put this line in your subroutine:

For example, let’s make the computer say “You turned me on, and I love you!” and maximize the Form1 window (so the human can see all that). Just put both of these lines in your subroutine:

Final steps

When you finish playing with your program, here’s what to do.

Make sure you see the subroutine you typed. (If you see Form1’s window instead, close that window by clicking its X button.)

Save If you like the program you created and want to save it on disk, click the Save All button. (It looks like a pile of 4 floppy disks. It’s near the screen’s top, below the word “Project”.)

If the computer says “Save Project”, do this:

For example, if you gave your program the name “Funmaker”, that process makes the computer create a folder called Funmaker and put it into the Projects folder (which is in the Visual Studio 2010 folder, which is in the Documents folder). That folder contains Funmaker.suo, Funmaker.sln, and another folder called Funmaker, which in turn contains many other files and folders.

Afterwards, if you make further changes to the program, click the Save All button again to save them.

New If you’re tired of working on a program and want to start inventing a different program instead, click the
New Project button (which is near the screen’s top-left corner, below the word “File”).

(If you didn’t save the previous program, the computer will say “save or discard changes”. If you want to save the previous program, click “Save” and answer any questions the computer asks about the program’s name; otherwise, click “Discard”.)

Eventually, the computer will say “New Project”. Double-click “Windows Forms Application”.

Exit When you finish using VB, click the X button that’s in the screen’s top right corner.

Open When you start using VB, look at the heading “Recent Projects” (which appears near the screen’s left edge). Below “Recent Projects”, you see a list of programs you saved. If you want to use or edit one of those programs, click that program’s name then click double-click Form1.vb (which is at the screen’s left edge). Either run the program again (by pressing F5) or edit the program’s commands (by double-clicking in the middle of the Form1 window).

Run the .exe file When the computer ran your program, it made an .exe file (called Funmaker.exe), which you can run again without going into Visual Basic. Here’s how:

Here’s another way to execute the Funmaker.exe program:

Registration

While you’re using Visual Basic Express, you might be interrupted by a window saying “Registration is required”. That means you haven’t registered Visual Basic Express yet.

You can use Visual Basic Express for 30 days without registering it. Before the 30 days run out, you should register it by clicking that window’s “Obtain a registration key online” button (or by clicking “Help” then “Register Product” then “Obtain a registration key online”).

After you click “Obtain a registration key online”, continue the registration procedure by following the instructions on the screen. Registration is free.

Registration is free. It consists of telling Microsoft your name, country, ZIP code (or other postal code), e-mail address, and what kind of e-mail you want Microsoft to send you about learning programming. You also create (or reuse) your Microsoft Windows Live account.

 

A letter can stand for a number, a string, or other things.

For example, x can stand for the number 47, as in this subroutine:

The top line (Dim x) warns the computer that x will stand for something. (The “Dim” comes from the word “Dimension”.)

The second line (x = 47) says x stands for the number 47. In other words, x is a name for the number 47.

The bottom line (Text = x + 2) makes the computer display x + 2. Since x is 47, the x + 2 is 49; so the computer will display 49. That’s the only number the computer will display; it will not display 47.

When you type that subroutine, make sure you include the top line (Dim x). If you forget to type that line, the computer will gripe by saying:

Jargon

A letter standing for something is called a variable (or name or identifier). A letter standing for a number is called a numeric variable. In that subroutine, x is a numeric variable; it stands for the number 47. The value of x is 47.

In that subroutine, the statement “x = 47” is called an assignment statement, because it assigns 47 to x.

A variable is a box

When you run that subroutine, here’s what happens inside the computer.

The computer’s random-access memory (RAM) consists of electronic boxes. When the computer encounters the line “x = 47”, the computer puts 47 into box x, like this:

box x                47

Then when the computer encounters the line “Text = x + 2”, the computer will display what’s in box x, plus 2; so the computer will display 49.

Faster typing

Instead of typing —

you can type just this:

Before the computer runs the program, the computer will automatically put spaces around the equal sign.

More examples

Here’s another subroutine:

The top line says y is a variable. The next line says y is 38. The bottom line says to display y - 2. Since y is 38, the
y - 2 is 36; so the computer will display 36.

Another example:

The top line says b is a variable. The next line says b is 8. The bottom line says to display b * 3, which is 8 * 3, which is 24; so the computer will display 24.

One variable can define another:

The top line says n and d are variables. The next line says n is 6. The next line says d is n + 1, which is 6 + 1, which is 7; so d is 7. The bottom line says to display n * d, which is 6 * 7, which is 42; so the computer will display 42.

Changing a value

A value can change:

The second line says k is 4, but the next line changes k’s value to 9, so the bottom line displays 18.

When you run that subroutine, here’s what happens inside the computer’s RAM. The second line (k = 4) makes the computer put 4 into box k:

box k                 4

The next line (k = 9) puts 9 into box k. The 9 replaces the 4:

box k                 9

That’s why the bottom line (Text = k * 2) displays 18.

String variables

A string is any collection of characters, such as “I love you”. Each string must be in quotation marks.

A letter can stand for a string:

The top line warns the computer that x will stand for something. The next line says x stands for the string “I love you”. The bottom line makes the computer display:

In that subroutine, x is a variable. Since it stands for a string, it’s called a string variable.

You can combine strings:

(When typing that example, you must leave a space before the ampersand, to avoid confusion.) Since the second line says x is “so”, the bottom line will make Text be “so” & “up” and display this:

If you insert a space by typing “ up” instead of “up”, like this —

the computer will display:

Long variable names

A variable’s name can be a letter (such as x) or a longer combination of characters, such as:

For example, you can type:

The computer will print:

The variable’s name can be as long as you wish: up to 255 characters! The name’s first character must be a letter; the remaining characters can be letters or digits. The computer ignores capitalization: it assumes that CityPopulationIn2001 is the same as citypopulationin2001.

Beginners are usually too lazy to type long variable names, so beginners use variable names that are short. But when you become a pro and write a long, fancy program containing hundreds of lines and hundreds of variables, you should use long variable names to help you remember each variable’s purpose.

In this book, I’ll use short variable names in short programs (so you can type those programs quickly) but long variable names in long programs (so you can keep track of which variable is which).

Here’s how to make a box appear suddenly on your screen.

Message box

Into any subroutine, you can insert this line:

When the computer runs the program and encounters that line, the computer suddenly creates a message box (a window containing a short message), which appears in front of all other windows (so they’re covered up) and contains this message: “Warning: your hair looks messy today”. The computer automatically makes the window be wide enough to include the whole message and be centered on the screen. When that window suddenly appears, the computer also beeps (to get the human’s attention) if you’re using Windows Vista (instead of Windows 7).

The window includes an OK button. When the human finishes reading the message, the human must click that OK button (or press Enter) to make the window go away.

After the window goes away, Form1 reappears and the computer continues running the rest of the program (including any lines below the MsgBox line). Form1 remains on the screen until the human clicks Form1’s X button, which closes the form and ends the program.

End program automatically To please the human, make the computer click Form1’s X button and end the program, by putting this command under the MsgBox line —

so your subroutine looks like this:

The top line makes the message box say “Warning: your hair looks messy today” then wait for the human to click OK. The bottom line ends the program (without requiring the human to click an X button).

Putting End under MsgBox makes the screen look like this:

Try it!

That End line is helpful. If you omit it and say just —

here’s what happens when the human runs the program:

Faster typing If you type just —

the computer will automatically change it to:

Add an icon To make the message box fancier, say vbExclamation, like this:

That makes the message box window include an exclamation icon (an exclamation point in a yellow triangle).

You can choose from 4 icons:

Math A message box can do math. For example, if you write a subroutine that says —

and then run the program (by pressing F5), the computer will create a message box that displays the answer, 6.

Input box

For a wild experience, type this subroutine:

Run the program (by pressing F5). Here’s what happens…

The InputBox line makes the computer suddenly creates an input box, which is a window letting the human type info into the computer. That window appears in front of all other windows (so they’re covered up) and is centered on the screen. It contains this prompt: “What is your name?” It also contains a white box (into which the human can type a response) and an OK button.

The computer waits for the human to type a response. When the human finishes typing a response, the human must click the OK button (or press Enter) to make the window go away.

Then Form1 reappears, and the computer makes x be whatever the human typed. For example, if the human typed —

x will be Joan. Then the Text line will make Form1 say:

To let the subroutine handle names that are long, maximize the Form1 window, by inserting this line —

so the subroutine becomes:

Numeric input To input a string, you’ve learned to say InputBox. To input a number, say InputBox but also say Val, to emphasize that you want the computer to produce a numeric value.

For example, this subroutine asks for your two favorite numbers and says their sum:

When you run the program (by pressing F5), the computer asks “What is the first number?”, waits for you to type it, and calls it x. Then the computer asks “What is the second number?”, waits for you to type it, and calls it y. Then the computer says the sum of the numbers. For example, if the first number was 7 and the second number was 2, the computer will display the sum:

In that program, if you accidentally omit each Val, the computer will think x and y are strings instead of numbers, so the computer will add the string “7” to the string “2” and display this longer string:

Predict your future This subroutine makes the computer predict your future:

When you run the program, the computer asks, “In what year were you born?” If you answer —

y will be the numeric value 1962, and the computer will correctly print:

Prices Suppose you’re selling tickets to a play. Each ticket costs $2.79. (You decided $2.79 would be a nifty price, because the cast has 279 people.) These lines find the price of multiple tickets:

Conversion These lines convert feet to inches:

When you run the program, the computer asks “How many feet?” If you answer —

the computer will say:

Trying to convert to the metric system? These lines convert inches to centimeters:

Nice day today, isn’t it? These lines convert the temperature from Celsius to Fahrenheit:

When you run the program, the computer asks “How many degrees Celsius?” If you answer —

the computer will say:

See, you can write the Guide yourself! Just hunt through any old math or science book, find any old formula (such as f = c * 1.8 + 32), and turn it into a program.

A subroutine is a list of commands you want the computer to obey. Here’s how to control which commands the computer obeys, and when, and in what order.

If

This subroutine makes the computer discuss the human’s age:

When that program is run (by pressing F5), the computer asks “How old are you?” and waits for the human’s reply. For example, if the human says —

the age will be 15. Then the computer will say:

After the human reads that message in the message box, the human should get out of the message box (by clicking the message box’s “OK” or pressing the Enter key). Then the computer will automatically close Form1.

Let’s make that subroutine fancier, so if the human is under 18 the computer will also say “You are still a minor”. To do that, just add a line saying —

so the subroutine looks like this:

For example, if the human runs the program and says —

the computer will say —

and then say:

(At the end of each sentence, the computer waits for the human to click the message box’s OK.)

If instead the human says —

the computer will say just:

In that program, the most important line is:

That line contains the words If and Then. Whenever you say “If”, you must also say “Then”. Don’t put a comma before “Then”. What comes between “If” and “Then” is called the condition; in that example, the condition is “age < 18”. If the condition is true (if the age is really less than 18), the computer does the action, which comes after the word “Then” and is:

Else Let’s teach the computer how to respond to adults.

Here’s how to program the computer so that if the age is less than 18, the computer will say “You are still a minor”, but if the age is not less than 18 the computer will say “You are an adult” instead:

In programs, the word “Else” means “otherwise”. That program’s If line means: if the age is less than 18, then print “You are still a minor”; otherwise (if the age is not less than 18), print “You are an adult”. So the computer will print “You are still a minor” or else print “You are an adult”, depending on whether the age is less than 18.

Try running that program! If you say you’re 50 years old, the computer will reply by saying —

and then (after you click “OK”):

Multi-line If If the age is less than 18, here’s how to make the computer say “You are still a minor” and also say “Ah, the joys of youth”:

Here’s a more sophisticated way to say the same thing:

That sophisticated way (in which you type 4 short lines instead of a single long line) is called a multi-line If (or a block If).

In a multi-line If:

In the middle of a multi-line If, you can say Else:

That means: if the age is less than 18, then say “You are still a minor” and “Ah, the joys of youth”; otherwise (if age not under 18) say “You are an adult” and “We can have adult fun”. The computer automatically unindents the word “Else”.

ElseIf Let’s make the computer do this:

Here’s how:

Different relations You can make the If clause very fancy:

In the If statement, the symbols =, <, >, <=, >=, and <> are called relations.

When writing a relation, mathematicians and computerists habitually put the equal sign last:

When you press the Enter key at the end of the line, the computer will automatically put your equal signs last: the computer will turn any “=<” into “<=”; it will turn any “=>” into “<=”.

To say “not equal to”, say “less than or greater than”, like this: <>.

Or The computer understands the word Or. For example, here’s how to type, “If age is either 7 or 8, say the word wonderful”:

That example is composed of two conditions: the first condition is “x = 7”; the second condition is “x = 8”. Those two conditions combine, to form “x = 7 Or x = 8”, which is called a compound condition.

If you use the word Or, put it between two conditions.

And The computer understands the word And. Here’s how to type, “If age is more than 5 and less than 10, say you get hamburgers for lunch”:

Here’s how to type, “If score is at least 60 and less than 65, say you almost failed”:

Here’s how to type, “If n is a number from 1 to 10, say that’s good”:

Immediate If Here’s a shortcut. Instead of saying —

you can say:

That line means:

That line is used in this subroutine:

The abbreviation IIf means “Immediate If”. It lets you do an If immediately, without have to type the words “Then” and “Else”.

Yes/no message box

Let’s make the computer ask, “Do you love me?” If the human says “Yes”, let’s make the computer say “I love you too!” If the human says “No”, let’s make the computer say “I don’t love you either!”

This subroutine accomplishes that goal:

But that subroutine has a flaw: what if the human types neither “yes” nor “no”? Instead of typing “yes”, what if the human types “YES” or “Yes” or “yeah” or “yep” or “yessiree” or just “y” or “certainly” or “I love you tremendously” or “not sure”? In those situations, since the human didn’t type simply “yes”, the computer will say “I don’t love you either!”, which is inappropriate.

The problem with that subroutine is it gives the human too many choices: it lets the human type anything in the input box.

To make sure the computer reacts appropriately to the human, give the human fewer choices. Restrict the human to choosing just Yes or No. Here’s how: show the human a Yes button and a No button, then force the human to click one of them. This subroutine accomplishes that:

The MsgBox line makes the computer create a message box saying “Do you love me?” A normal message box contains an OK button, but vbYesNo makes this be a yes/no message box instead (which contains Yes and No buttons instead of an OK button).

If the human clicks the Yes button, the subroutine makes the computer say “I love you too!” If the human does otherwise (by clicking the No button), the computer says “I don’t love you either!”

Long programs While running a long program, the computer should occasionally ask whether the human wants to continue. To make the computer ask that, insert this line:

That line creates a yes/no message box asking “Do you want to continue?” If the human clicks the No button, the program will end (and the computer will automatically click the program’s X button).

Select

Let’s turn your computer into a therapist!

To do that, make the computer ask the patient “How are you?” and let the patient type whatever words the patient wishes. Just begin the subroutine like this:

That makes the computer ask “How are you?” and makes the patient’s response be called the feeling.

Make the computer continue the conversation as follows:

To accomplish all that, you can use a multi-line If:

Then end the whole program:

Instead of typing that multi-line If, you can type this
Select statement instead, which is briefer and simpler:

Like a multi-line If, a Select statement consumes several lines. The top line of that Select statement tells the computer to analyze the feeling and Select one of the cases from the list underneath. That list is indented and says:

While you’re typing the Select statement, the computer automatically indents the lines for you and automatically types “End Select” underneath.

Complete subroutine Here’s a complete subroutine:

The InputBox line makes the computer ask the patient, “How are you?” The next several lines are the Select statement, which makes the computer analyze the patient’s answer and print “That’s good!” or “Too bad!” or else “I feel the same way!”

Regardless of what the patient and computer said, that subroutine’s bottom MsgBox line always makes the computer end the conversation by saying:

In that program, try changing the strings to make the computer say smarter remarks, become a better therapist, and charge even more money.

Fancy cases You can create fancy cases:

When typing a Case statement, don’t bother typing the word “Is”. The computer will type it for you automatically.

Exit Sub

To make the computer skip the bottom part of your subroutine, say Exit Sub, like this:

When you run that program (by pressing F5), the computer will say “I love the company president” but then exit from the subroutine, without saying “I love him as much as stale bread”. The computer will say just:

Suppose you write a subroutine that displays many messages, and you want to run the program several times (so several of your friends see the messages). If one of your friends would be offended by the last few messages, send that friend an abridged subroutine! Here’s how: put Exit Sub above program part that you want the computer to ignore.

“Exit Sub” versus “End”. Instead of saying “Exit Sub”, you can say “End”. Here’s the difference:

While you’re creating or editing a Visual Basic program, you see tabs near the screen’s top-left corner. Try clicking those tabs now:

Try this experiment.…

Click the “Form1.vb [Design]” tab, so you see the Form1 window itself. Then click (just once) in the middle of the Form1 window.

Then the screen’s bottom-right corner should show a list, whose title is:

If you don’t see that list yet, press the F4 key then try again to click in the middle of the Form1 window.

That list is called Form1’s main property list (or property window). It looks like this:

(The screen shows part of the list. To see the whole list, use the list’s scroll arrows.)

Text

The top of Form1’s window normally says “Form1”. That’s called the window’s title (or caption or text). Instead of making the title say “Form1”, you can make it say “Results” or “Payroll results” or “Mary’s window” or “Fun stuff” or “Hey, I’m a funny window” or anything else you wish!

To make Form1’s title say “Fun stuff”, you can put this line in Form1’s subroutine —

but here’s an easier way:

Try that now! It makes the top of Form1 say “Fun stuff” immediately (or when you press Enter or F5 or click the Form1 window or the “Form1.vb [Design]” tab).

Color

Normally, the Form1 window’s middle is a big blank area that’s nearly white (a color called Control, which is very light gray). To make it red instead, you can put this line in Form1’s subroutine —

but here’s an easier way:

Try that now! It makes Form1’s background color become Red instantly.

Maximize

The Form1 window is normally medium-sized. To maximize it, you can use 3 methods.

Manual method While the program is running (because you pressed F5), you can manually click the Form1 window’s maximize button. That maximizes the window but just temporarily: when you finish running the program (by clicking the Form1 window’s X button), the computer forgets about maximization. The next time you run the program, it will not be maximized, unless you click the maximize button again.

Equation method Insert this equation in Form1’s subroutine:

Property-list method In Form1’s main property list, click WindowState then WindowState’s down-arrow then Maximized. That makes the property list’s WindowState line become:

When you run the program (by pressing F5), Form1’s window will be maximized.

Refuse to maximize

Instead of maximizing the Form1 window, you can do just the opposite: you can prevent the user from maximizing. Here’s how.…

In Form1’s main property list, click MaximizeBox then press the F key (which means “False”). That makes the property list’s MaximizeBox line become:

That make Form1’s maximize button (which is also called the maximize box) be grayed out while the program runs; the maximize button will become gray instead of black-and-white. That grayed-out button will ignore all attempts to be clicked, so the window will refuse to maximize.

Resize

Normally, Form1 is 300 pixels wide and 300 pixels tall. Here’s how to adjust that size.…

Property-list method In Form1’s main property list, click Size, then change “300, 300” to the size you wish, by editing those numbers. For example, if you want Form1 to be 500 pixels wide and 400 pixels tall, change the size to “500, 400”. The first number is the form’s width; the second number is the form’s height.

The biggest permissible size is the size of your whole screen. For example, if your screen is traditional (17-inch CRT, set at a resolution of 1024-by-768), the biggest permissible size for you is “1024, 768”. If you want Form1 to be half as wide and half as tall as that, choose “512, 384”.

The smallest permissible size is “124, 36”. That’s barely enough to show Form1’s fundamental buttons (close, maximize, and minimize), not much else!

If you request a size that’s very big (almost as big as the screen), Form1 won’t look that big until you run the program (by pressing F5).

Drag method While the program is running (because you pressed F5), you can change Form1’s size by dragging its bottom right corner. That changes the size just temporarily: when you finish running the program (by clicking Form1’s X button), the computer forgets how you dragged Form1’s corner, and Form1 reverts to its previous size.

Here’s how to change Form1’s size so the computer remembers the new size:

Refuse to resize

In Form1’s main property list, the FormBorderStyle line normally says:

Try this experiment: click FormBorderStyle then FormBorderStyle’s down-arrow then “FixedToolWindow”, so the line becomes:

That prevents stupid humans from changing Form1’s size. When a human runs the program (by pressing F5), Form1’s window will have no maximize button, no restore-down button, no minimize button, and no resizable edges. Form1 stays the size you specified in the property list (such as the property list’s Size line), so stupid humans can’t mess up your beautiful design (unless they edit your subroutine or property list).

Form position

Here’s how to adjust Form1’s position.…

Property-list method In Form1’s main property list, click StartPosition then StartPosition’s down-arrow. You see this list of choices:

Click a choice now. You’ll see the effect later (when you press the F5 key to run the program).

The computer assumes you want “WindowsDefaultLocation” unless you click a different choice instead.

All those inch measurements are approximate and depend on your screen’s size.

Drag method While the program is running, you can move Form1 by dragging its title bar (the blue horizontal bar that’s at Form1’s top and typically says “Form1”). That moves Form1 just temporarily; when you finish running the program (by clicking Form1’s X button), the computer forgets how you dragged Form1, and Form1 reverts to its previous position.

Opacity

Normally, Form1 is completely opaque: while the program is running, Form1 completely blocks the view of anything behind it.

To have fun, reduce Form1’s opacity: in Form1’s main property list, click Opacity, then change “100%” to “75%”. When you run the program (by pressing F5), Form1 will be just partly opaque; it will be partly transparent, so you can see, faintly, what’s behind the form.

If you make the opacity even lower — 50% or 25% — Form1 will be hardly opaque at all — it will be very transparent — so you can easily see what’s behind it, as if Form1 were just a ghost.

Try making the opacity be 90%.

Opacity doesn’t work well if your Windows version is old (Windows XP) or stripped-down (Windows Vista Basic or Windows 7 Starter), since those Windows versions lack Windows Aero (which makes windows partly transparent).

You’ve learned how to create and manipulate an object called “Form1”. You can create other objects also, by using the toolbox.

See the toolbox

To see the toolbox — and start fresh — exit from Visual Basic (by clicking Visual Basic’s X button), then go back into Visual Basic by doing this:

At the screen’s left edge, you’ll see the word “Toolbox”.

If you’re lucky, you’ll see this:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

If you see just the word “Toolbox” but none of those other words, make them appear by clicking “Toolbox”, then make them stay on the screen permanently by clicking the push pin, which is just left of the toolbox’s X.

Make sure the triangle left of “All Windows Forms” has a white middle. (If the triangle is solid black instead, click the triangle to make its middle white.)

Make sure the triangle left of “Common Controls” is solid black. (If that triangle has a white middle instead, click the triangle to make it solid black.)

Each object in the toolbox is called a tool.

The complete toolbox is too tall to fit on your screen. You see just the toolbox’s beginning. Whenever you want to see the rest of the toolbox (which includes many dozens of tools), click the toolbox’s scroll-down arrow (at the toolbox’s bottom-right corner).

Button

Try this experiment. Double-click the Button tool. That makes a button appear in Form1’s middle, near Form1’s top-left corner (or near a previous button). The button is a rectangle and says “Button1” on it.

(If you wish, drag that button to a different place in Form1. You can also change the button’s size by dragging its 9 square handles. But for your first experiment, just leave the button where the computer put it.)

The button says “Button1” on it. Just for fun, let’s make it say “Click me” instead. To do that, click Text (in the property list) and type “Click me”, so the property list’s Text line becomes:

That makes the button’s text become “Click me” (instead of “Button1”).

Notice that the property list concerns the button and its text (instead of Form1’s text), because the button is highlighted.

Let’s write a program so if a human clicks the button (which says “Click me”), Form1 will say “Thanks for the click”. To do that, double-click the button. The double-clicking tells the computer you want to write a subroutine about that object (the button).

The computer starts writing the subroutine for you. The computer writes:

Insert this line in the middle of the subroutine —

so the subroutine looks like this:

That subroutine tells the computer that when Button1 is clicked, the computer should say “Thanks for the click” on Form1.

Try it: run that program (by pressing F5). You’ll see Form1 with a button on it that says “Click me”. If you click the button, the subroutine makes Form1 say “Thanks for the click”.

In that subroutine, the computer assumes you want the text “Thanks for the click” to be on Form1, not on the button. If you want that text to be on the button instead, say Button 1’s Text instead of just Text. To say Button 1’s Text, type Button1.Text, so the subroutine looks like this:

But to fit “Thanks for the click” onto the button, you must widen the button, by doing this:

Two buttons Let’s write a program that has two buttons! Let’s make the first button be called “Red” and the second button be called “Blue”. If the human clicks the “Red” button, let’s make Form1 turn red; if the human clicks the “Blue” button, let’s make Form1 turn blue.

To do all that, start a new program as follows:

In the Toolbox, double-click the Button tool. A command button appears in Form1 and is called Button1. In the property list, click Text then type “Click here for red” (and press Enter), so the property list’s Text line becomes:

That tries to make the button’s text become “Click here for red”. To fit all that text onto the button, widen the button (by dragging one of its handles).

In the Toolbox, double-click the Button tool again. That makes another command button appear in Form1 and be called Button2. Unfortunately, the Button2 button covers up the Button1 button, so you can’t see the Button1 button. Drag the Button2 button out of the way (toward the right), so you can see both buttons side-by-side.

The Button2 button should be highlighted. (If it’s not highlighted, click it to make it highlighted.) In its property list, change its Text from “Button2” to “Click here for blue” (by clicking Text then typing “Click here for blue” and pressing Enter). Widen the Button2 button (by dragging one of its handles) so it shows all of “Click here for blue”.

Now your screen shows Form1 with two buttons on it. The first button says “Click here for red”. The second button says “Click here for blue”.

Double-click the “Click here for red” button, and write this subroutine for it:

That subroutine says: clicking that button will make Form1’s background color be red.

Move that subroutine out of the way (by clicking the “Form1.vb [Design]” tab, so you can see Form1.

Double-click the “Click here for blue” button, and write this subroutine for it:

While you’re writing that subroutine, you’ll see the other subroutine above it. Altogether, you see:

Then run the program by pressing F5. Here’s what happens.…

You see Form1 with two buttons on it. The first button says “Click here for red”; if you click it, Form1 turns red. The other button says “Click here for blue”; if you click it, Form1 turns blue.

Try clicking one button, then the other. Click as often as you like. When you get tired of clicking, end the program (by clicking Form1’s X button).

Where to put buttons A good habit is to put buttons side-by-side, in Form1’s bottom right corner. That way, the buttons won’t interfere with any other objects on Form1.

Exit button To stop running a typical program, you have to click its X button. Some humans don’t know to do that. To help them, create a button called “Exit”, so that clicking it will make the computer exit from the program.

To do that, create an ordinary button; but make the button’s text say “Exit” (or anything else you prefer, such as “Quit” or “End” or “Abort” or “Close” or “Click here to end the program”), and make the button’s subroutine say End, like this:

Put that Exit button in Form1’s bottom-right corner.

Check box

A check box is a small gray square, with text to the right of the square. At first, the gray square has nothing inside it: it’s empty. While the program runs, clicking the square makes a green check mark (a) appear in the square. If you click the square again, the check mark disappears.

To create a check box, double-click the CheckBox tool. That makes a check box appears in Form1. Drag the check box wherever you wish.

The first check box’s text is temporarily “CheckBox1”; to change that text, click Text (in the property list) and type whatever text you wish. At the end of your typing, press Enter. Suggestion: if you want to type a lot of text, do this instead:

If you want the computer to react immediately to whether the check box is checked, give the check box this subroutine:

Dressed example For example, this subroutine makes the computer say “I am dressed” if the check box just became checked but say “I am naked” if the check box just became empty:

When that program runs, the check box starts by being empty. Clicking the check box makes you see a and makes the computer say “I am dressed”. The next time you click the check box, the a disappears from the box, so the box becomes empty and the computer say “I am naked”. Clicking the check box again makes the a reappear and makes the computer say “I am dressed”.

Here’s how to type that subroutine fast:

Multiple check boxes Form1 can contain many check boxes. The human can check several at the same time, so that several of the boxes contain check marks simultaneously.

Although you can put buttons and check boxes wherever you wish, it’s customary to arrange buttons horizontally (so the second button is to the right of the first) but arrange check boxes vertically (so the second check box is below the first). The check boxes (and their texts) form a vertical list of choices.

OK button If Form1 contains several check boxes, you should typically delay the computer’s reaction until the human has decided which boxes to check, has checked all the ones desired, and has clicked an OK button to confirm that the correct boxes are checked.

To do that, make the check boxes have no subroutines. Instead, create an OK button in Form1’s bottom-right corner (by creating a button there and making its text be “OK”), then make the OK button’s subroutine look like this:

That subroutine says: when the OK button is clicked, notice which check boxes are checked and react appropriately.

For example, let’s make a program that alters Form1’s appearance, to make it red or maximized or red maximized or return to normal. Here’s how to do all that:

Radio button

A radio button resembles a check box but looks and acts like the button on an old-fashioned radio, because of these differences.…

Like checkboxes, radio buttons are arranged vertically (so the second radio button is below the first). The radio buttons (and their titles) form a vertical list of choices.

When the human starts running your program, the first radio button (which is RadioButton1) has a blue dot inside the gray circle, and the computer automatically does RadioButton1’s subroutine (even if the human hasn’t clicked RadioButton1’s button yet).

Afterwards, if the human clicks a different radio button, here’s what happens:

If you want the computer to react immediately to whether the radio button has the blue dot, give the radio button this subroutine:

3-color example For example, let’s write a program that has 3 radio buttons, labeled “Red”, “Blue”, and “Green”. While the program is running, if the human switches from “Red” to “Blue” (by clicking “Blue” after having clicked “Red”), let’s make the program say “Sorry you don’t like red anymore” and make Form1 become blue. Let’s make the program act similarly for switching between other pairs of colors.

To do that, maximize Form 1 (by making its WindowState property be Maximized) and create the 3 radio buttons (labeled “Red”, “Blue”, and “Green”). Then give the “Red” button (which is RadioButton1) this subroutine:

That subroutine runs just when the human changes the Red radio button’s appearance (by clicking it or unclicking it):

Here’s how to type that subroutine fast:

To finish the program, type this subroutine for the “Blue” button (which is RadioButton2) —

and this subroutine for the “Green” button (which is RadioButton3):

3-city example For a similar example, let’s write an airplane program that has 3 radio buttons, labeled “Los Angeles”, “Dallas”, and “New York”. While the program is running, if the human switches from “Los Angeles” to “Dallas” (by clicking “Dallas” after having clicked “Los Angeles”), let’s make the program say “You’ve left Los Angeles” and “Welcome to Dallas”. Let’s make the program act similarly for traveling between the other cities.

To do that, create the 3 radio buttons (labeled “Los Angeles”, “Dallas”, and “New York”). Then give the “Los Angeles” button (which is RadioButton1) this subroutine:

That subroutine runs just when the human changes the Los Angeles radio button’s appearance (by clicking it or unclicking it):

To finish the program, type this subroutine for the “Dallas” button (which is RadioButton2) —

and this subroutine for the “New York” button (which is RadioButton3):

OK button When the human clicks a radio button, the computer can react to the click immediately, but that might startle and upset the human. If you want to be gentler, delay the computer’s reaction until the human also clicks a general OK button, which confirms the human’s desires.

To do that, make the radio buttons have no subroutines, so nothing will happen when those buttons are clicked. In Form1’s bottom-right corner, create an ordinary button whose text says “OK” and whose subroutine looks like this:

That subroutine says: when the OK button is clicked, notice which radio button was clicked and react appropriately.

Label

Form1 has two main parts. One part is a blue bar across Form1’s top: it includes Form1’s minimize button, maximize button, close button, and text. The other part (Form1’s middle) is a big light-gray box: it includes objects you created, such as ordinary buttons, check boxes, and radio buttons.

In Form1’s middle, let’s type this text:

To do that, double-click the Label tool. That makes the word “Label1” appear in Form1’s middle. Drag “Label1” to the spot in Form1 where you wish to begin typing. To change “Label1” to “I love you”, click Text (in Label1’s property list) then type “I love you”, so the property list says:

At the end of that typing, press Enter. Then “Label1” becomes “I love you”, so “I love you” is in Form1’s middle.

Multi-line text Instead of making Form1’s middle say just “I love you”, let’s make it say:

Here’s how:

Text equation Here’s a different way to make Form1’s middle say “I love you”.

Create a label (by double-clicking the Label tool). Tell the computer you want to write a subroutine for Form1 (by double-clicking in Form1 but not in the label). Put this line in Form1’s subroutine:

That means: the label’s text is “I love you.” That line makes Form1’s subroutine become this:

When you run the program (by pressing F5), the computer will run that subroutine and make Form1’s middle say:

If instead you want the Form1’s middle to say —

change the Text line to this:

That makes the computer type “I love you” then press key #13 (which is the Enter key) then type “You turned me on”. Instead of that long Text line, you can give this pair of shorter Text lines:

In that pair of lines, the first line makes the Text be “I love you”; the next line changes the Text to become all that, combined with Chr(13) and “You turned me on”.

Math Let’s make Form1’s middle say the answer to 4 + 2.

To do that, create a label (by double-clicking the Label tool). Tell the computer you want to write a subroutine for Form1 (by double-clicking in Form1 but not in the label). Put this line in Form1’s subroutine:

That line means: Label1’s text is the answer to 4 + 2. That line makes Form1’s subroutine become this:

When you run the program (by pressing F5), the computer will run that subroutine and write the answer (6) in Form1’s middle.

To make Form1’s middle say the answer to 4 + 2 and, on the next line, say the answer to 48 + 3, you can put this line in Form1’s subroutine —

or give this pair of lines instead:

In that pair of lines, the first line makes the Text be the answer to 4 + 2; the next line changes the Text to become all that, combined with Chr(13) and the answer to 48 + 3.

List box

A list box is a big white box that contains a list of choices, such as these color choices —

or these country choices —

The list can be short (2 or 3 choices) or tall (hundreds of choices). If the list is too tall fit in the box, the computer will automatically add scroll arrows so humans can scroll through the list.

To create a list box, double-click the ListBox tool. A list box (big white box) appears in the middle of Form1. Drag the list box wherever you wish.

The first list box is called ListBox1. Inside that list box, you temporarily see the word “ListBox1”, but you should put your own list of choices there instead, by using this method —

or this alternate method:

Then on Form1, you see the list box containing your choices.

By dragging the box’s handles, try to make the box just tall enough to hold all the choices. (If it isn’t tall enough, the computer automatically adds scroll arrows so humans can scroll through the list while the program runs.)

By dragging the box’s handles, make the box just wide enough to hold the widest choice.

Select one You can give List1 this kind of subroutine:

Here’s a shorter way to type the subroutine:

If you want the action to be delayed until the human clicks an OK button, do this:

Select multi If you want to let the human select several items from the list (instead of just one item), do this:

Label Next to your list box, you should put some text, explaining the list box’s purpose to the human. To put the text there, create a label with that text (by double-clicking the Label tool), and drag the label until it’s next to your list box.

Text box

You already learned that Form1’s subroutine can contain this line:

When you run the program, that line makes the computer create an input box. The input box is a pop-up window containing a message (“What is your name?”), a wide white box (in which the human types a response), and an OK button (which the human clicks when finished typing).

That technique works adequately but gives you no control over the size or position of its objects (the window, message, white response box, and OK button).

To be more professional, get control by creating a text box instead. Here’s how.

Double-click the TextBox tool. That creates a text box (a white box in which the human can type a response). Drag it wherever you wish. Adjust its size by dragging its handles.

Above the box (or left of it), put a label (by double-clicking the Label tool). Make the label contain a message (such as “What is your name?”).

Below the box (or right of the box), create an OK button (a button whose text says “OK”). Make the OK button’s subroutine include these lines —

and anything else you want the computer to do, such as:

Form1 can contain several text boxes. For example, you can include:

That makes Form1 be truly a form to fill in! Create just one OK button to handle all those text boxes, so the human clicks the OK button after filling in the entire form.

Password character If you want the human to type a password into a text box, do this: in the text box’s property list, click PasswordChar then type an asterisk (the symbol *). That makes the box show asterisks instead of the characters the human is typing. That prevents enemies from discovering the password by peeking over the human’s shoulder.

MultiLine The typical text box holds just one line of text. To let your text box handle several lines of text well, make 3 adjustments:

Rich-text box

Instead of double-clicking the TextBox tool, try double-clicking the RichTextBox tool. It creates a text box that’s already tall, MultiLine (so the human can type many lines of text in the box), with a vertical scroll bar (which appears when the human types more lines than can fit in the box) and the ability to handle formatted text (which is called rich text). That box is called RichTextBox1.

For best results, make the box even taller and wider (by dragging its bottom-right corner).

In that box, the human can type a number, or a word, or a sentence, or a paragraph, or several paragraphs (by pressing the Enter key at the end of each paragraph), or a whole essay! What the human types in that box is called a document.

For example, if you want to invent your own word-processing program, the first step is to create a rich-text box for the human to type the words into.

Improve the rich-text box Here are 2 popular ways to improve how a rich-text box works:

Number box

To make the computer wait for the human’s response, you learned you can create a text box (by double-clicking the TextBox tool) and an OK button whose subroutine includes these lines:

If you want to force the human to type a number instead of words, create a number box instead of a text box. Here are the details.…

Double-click the NumericUpDown tool. That creates a number box (a white box in which the human can type a number). Drag it wherever you wish. Adjust its width by dragging its handles.

Above the box (or left of it), put a label (by double-clicking the Label tool). Make the label contain a message (such as “How many children do you have?”).

Below the box (or right of the box), create an OK button (a button whose text says “OK”). Make the OK button’s subroutine include these lines —

and anything else you want the computer to do, such as:

When the human runs the program, the human sees the number box. That box temporarily has 0 in it, but the human can change that number by retyping it or by clicking the box’s up-arrow (which increases the number) or down-arrow (which decreases the number). When the human has changed the number to what the human wishes, the human clicks the OK button, whose subroutine makes x become the human’s number.

Alter the box’s properties Normally, the number box refuses to let the human say any number over 100. If you want it to permit numbers up to 500, make its property list’s Maximum line say 500. If you want it to permit just numbers up to 20, make its Maximum line say just 20. If you want to encourage the human to type a number that’s small, make the box be narrow (by adjusting its handles).

Normally, the number box refuses to let the human say any number below 0. If you want it to permit numbers down to minus 500, make the property list’s Minimum line say -500. If you want it to require the number to be at least 3, make its Minimum line say 3.

Normally, the number box refuses to accept decimals. If you want it to permit 2 digits after the decimal point (so the human can type dollars-and-cents), make the property list’s DecimalPlaces line say 2.

The number box normally begins displaying the number 0. If you want it to begin by displaying the number 5 instead, make the property list’s Value line say 5.

By adjusting those properties (Maximum, Minimum, DecimalPlaces, Value, and the box’s width), you can encourage the human to be reasonable.

Combo box

A combo box is a fancy text box that includes a list of suggested responses.

To create a combo box, double-click the ComboBox tool. That creates a combo box. Like a text box, it’s a white box in which the human can type a response; but the combo box’s right edge shows a down-arrow, which the human can click to see a list of suggested responses.

Drag the combo box wherever you wish.

Click the box’s right-arrow (which is near the box’s top-right corner) then “Edit Items”. Type your list of suggested responses, such as:

(Press Enter at the end of each line.) When you’ve finished typing the whole list, click “OK” then click in the combo box.

Above (or left of) the box, put a label (by double-clicking the Label tool). Make the label contain a prompt (an instruction to the human about what to put into the box).

Below (or right of) the box, create an OK button (a command button whose caption is “OK”). Make the OK button’s subroutine include these lines —

and anything else you want the computer to do, such as:

Drop-down style In combo box’s property list, click DropDownStyle then DropDownStyle’s down-arrow. You see 3 styles:

Click whichever style you wish. If you don’t choose otherwise, the computer assumes you want “DropDown”. That works as I described: the human can type anything into the box, and the suggestion list appears just if the human clicks the box’s down-arrow.

If you choose “Simple” instead, the human can still type anything into the box, and the suggestion list always appears (without requiring a down-arrow click) if you make the combo box tall enough to hold the list.

If you choose “DropDown List” instead, the human cannot type into the box; the human is required to choose from the suggestion list, which appears when the human clicks the box.

Picture box

Here’s how to make Form1 show a picture.

First, enlarge Form1 (by dragging its bottom-right corner), to let it hold a big picture better.

Then double-click the PictureBox tool. That puts a box in Form1’s middle, near Form1’s top-left corner.

Enlarge that box (by dragging its bottom-right corner), to let it hold a big picture better. If you want the box to be smaller than Form1 (so Form1 can hold other objects also), drag the box where you wish (by pointing at the box’s middle, the dragging).

Click the box’s right-arrow (which is near the box’s top-right corner) then “Choose Image” then the bottom “Import” button then “Pictures” (which is on the left). That shows what’s in your hard disk’s Pictures folder.

Double-click the picture you want (after clicking or double-clicking any folders it’s buried in). For example, you can try double-clicking the “Sample Pictures” icon (which Windows has put in your Pictures folder) then “Penguins” (Windows 7’s photo of a penguin trio) or “Annie in the Sink” (Windows Vista’s photo of Annie the cat, sitting in a sink).

You see a bigger view of the picture (or its top-left corner). Click “OK”.

Click the Size Mode box’s down-arrow. You see this menu:

If the picture is bigger than the box, here’s what those choices mean.

The computer assumes you want “Normal”. If you prefer a different choice (such as “Zoom”), click it.

Should you dock? If you click “Dock in parent container”, the box will expand to fill Form1. (If you regret that expansion, undo it by clicking “Undock in parent container”.)

Add a form

Besides Form1, you can create extra forms, called Form2, Form3, Form4, etc. To create an extra form, click the Add New Item button (which is near the screen’s top, under the words “Edit” and “View”) then double-click the Windows Form icon.

For example, let’s make a button (on Form1) so that when you click that button, Form2 suddenly appears and says “I love you”. Here’s how.…

Start a new program (so you have a blank Form1).

Create Form2, by doing this:

When you run the program (by pressing F5), you see Form1, which contains a button saying “Click me”. If you click that button, the computer displays Form2, which covers Form1 and says “I love you”.

To stop running the program, close the Form2 window (by clicking its X button) then close the Form1 window (by clicking its X button).

Web browser

Here’s how to make a form’s middle show a Web page.

Create a blank form. (For a quick, fun experiment, you can use Form1, though in a practical program you’d use another form instead, such as Form2.) Make that blank form be maximized (by making its property list’s WindowState line say “Maximized”) or at least rather big (by making its property list’s Size line have rather big numbers).

Double-click the WebBrowser tool. That makes the form’s entire middle be devoted to the Web and be called WebBrowser1. In WebBrowser1’s property list, click “Url” then type the Web address you want the form to show (such as “www.yahoo.com”).

When you run the program (by pressing the F5 key), the form’s middle will show that Web page (or as much of it as will fit in the form’s middle, accompanies by scroll arrows).

Timer

To make the computer pause, use the Timer tool. Here are examples.

I love you!!!!!!!!!! Here’s how to make the computer say “I love you”, then pause, then add an exclamation point (so you see “I love you!”), then pause, then add another exclamation point (so you see “I love you!!”), then keep repeating that process, so you eventually see “I love you!!!!!!!!!!” and beyond!

Make Form1’s Text begin as “I love you” by doing this:

The next step is to say “add an exclamation point after pausing”. To deal with pausing, you must use the Timer tool. Here’s how.…

Look at the toolbox (which is at the screen’s left side and shows the tools). Using the toolbox’s scroll-down arrow, scroll down until you see a heading called “Components”.

Left of that heading, you see a triangle. That triangle should be solid black. (If the triangle has a white middle instead, click the triangle to make it solid black.)

Under the heading “Components”, you should see the Timer tool. Double-click it. That puts a Timer1 icon below Form1.

At the screen’s bottom-right corner, you see Timer1’s property list, which looks like this:

In that property list, click “Interval” then type 2000, so the Interval line becomes this:

That makes each pause be 2000 milliseconds (which is 2000 “thousands of a second”, which is 2 seconds).

In that property list, click “Enabled” then press the T key, so the Enabled line becomes this:

That turns the timer on, so it works.

Double-click the Timer1 icon, so you can write Timer1’s subroutine. Type this line in Timer1’s subroutine:

That makes the Text (of Form1) lengthen, by having an extra “!” added. Typing that line makes Timer1’s subroutine become this:

When you run the program (by pressing F5), the computer will show Form1 saying “I love you”, then pause for the next clock tick (the interval between ticks being 2000 milliseconds), then do Timer1’s subroutine (which turns “I love you” into I love you!”), then pause for the next clock tick, then do again Timer1’s subroutine (which turns “I love you!” into “I love you!!”), then pause for the next clock tick, then do again Timer1’s subroutine (which turns “I love you!!” into “I love you!!!”), then keep repeating that process, so you eventually see “I love you!!!!!!!!!!” and beyond. When the exclamation points become too numerous to fit in Form1’s title area, the computer changes the extra exclamation points to “…”. The program keeps running until you stop it (by clicking Form1’s X button).

If you want the exclamation points to come faster, make the interval shorter, by making Timer1’s Interval be less than 2000 milliseconds. For example, try making the Interval be 1000 milliseconds (which is 1 second), or 500 milliseconds (which is half a second), or 1 millisecond (which is almost instantaneous).

If you want the computer to add just one exclamation point and then relax (without adding further exclamation points), make Timer1’s subroutine become this:

That subroutine says: when the clock ticks, add an exclamation point to the text but then disable the timer, so no further exclamation points will be added.

To play a joke on a human, make Timer1’s Interval be 3000 (so the computer will pause 3 seconds before giving the joke’s punch line) and make Timer1’s subroutine become this:

That subroutine says: when the clock ticks (after 3 seconds), make the Text change from “I love you” to “I love your mother!” then disable the timer (because the joke’s timing is done).

Try making Timer1’s subroutine become this instead:

That subroutine says: when the clock ticks (after 3 seconds), make the Text change from “I love you” to “I’m happy when you’re gone”.

Count the seconds Here’s how to make Form1 count how many seconds have elapsed, so Form1 begins by saying 0, then a second later says 1, then a second later says 2, etc.

Make Form1’s Text begin at 0 by doing this:

In the toolbox (which at the screen’s left side and shows the tools), find the Timer tool (by scrolling down to “Components”, clicking any + sign left of “Components”, then scrolling down further). Double-click that Timer tool. That puts a Timer1 icon below Form1.

In Timer1’s property list (which is at the screen’s bottom-right corner), click “Interval” then type 1000, so you see this line:

Click “Enabled” then press the T key, so the Enabled line becomes this:

Double-click the Timer1 icon. Type this subroutine for Timer1:

That increases the text’s number, by adding 1 to it.

When you run the program (by pressing F5), Form1’s Text begins as 0 but increases to 1, then 2, then 3, etc.

Tell the date and time Here’s how to make Form1 act as a clock, so it tells you the date and time and updates itself every second!

Create a Timer1 icon (by double-clicking the Timer tool, which is in the toolbox under “Components”). In Timer1’s property list (which is at the screen’s bottom-right corner), make the “Interval” be 1000 and make “Enabled” be True.

Double-click the Timer1 icon. Type this subroutine for Timer1:

That makes the text become a message such as this:

You’ll see such a message when you run the program (by pressing F5). Since you set the Interval to 1000 milliseconds (which is 1 second), that text will correct itself every second.

Switch to blue Here’s how to make Form1 begin as red but then, after a pause, become blue.

Make Form1 begin as red by doing this:

Create a Timer1 icon (by double-clicking the Timer tool, which is in the toolbox under “Components”). In Timer1’s property list (which is at the screen’s bottom-right corner), make the “Interval” be 2000 and make “Enabled” be True.

Double-click the Timer1 icon. Type this subroutine for Timer1:

When you run the program (by pressing F5), Form1 begins as red but switches to blue (after a delay of 2000 milliseconds, which is 2 seconds).

Let’s make the subroutine fancier, so Form1 keeps alternating between red and blue. We’ll make Form1 start as red, then switch to blue, then switch back to red, then switch back to blue, then switch back to red, etc., forever. To do that, change the subroutine line to this:

It says the BackColor becomes this: if the BackColor was Red, then it becomes Blue, else it becomes Red.

Color dialog

Here’s how to let the human pick a color for Form1.

Look at the toolbox (which is at the screen’s left side and shows the tools). Using the toolbox’s scroll-down arrow, scroll down until you see a heading called “Dialogs”.

Left of that heading, you see a square. That square should contain a minus sign. (If it contains a plus sign instead, change the plus sign to a minus sign by clicking it.)

Under the heading “Dialogs”, you should see the ColorDialog tool. Double-click it. That puts a ColorDialog1 icon below Form1 and lets Form1’s subroutine mention “ColorDialog1”.

Double-click Form1. Write this Form1 subroutine:

When you run the program (by pressing F5), the subroutine’s top line makes the computer show the human the color dialog box, which contains 48 colors (plus a feature to let the human invent custom colors). When the human clicks one of the 48 colors (or a custom color) and then clicks “OK”, the subroutine’s bottom line makes Form1’s background color become the color the human chose.

While viewing the color dialog box, here’s how the human can create a custom color:

 

 

 

 

 

 

 

 

 

 

 

Here are some hints to help you master programming.

Stop debugging

While your program is running, you can interrupt it by clicking the Stop Debugging button (which is a square at the screen’s top center, to the right of the Start Debugging triangle).

The computer refuses to let you edit a program that’s in the middle of running. If you try to edit a program but the computer ignores your editing, that’s because your program is still in the middle of running. Stop the program from running (by clicking the Stop Debugging square, which is blue), then try again to edit your program.

Avoiding Dim

If x is a variable, you’re supposed to warn the computer by saying:

If you’re too lazy to say “Dim” for each variable, say
Option Explicit Off at your program’s top, so your program looks like this:

To type “Option Explicit Off” up there, do this:

The “Option Explicit Off” prevents the computer from griping about missing Dim lines. It makes your program’s variables work even if you don’t say “Dim”. But it also prevents the computer from warning you about using variables in ridiculous ways. Say “Option Explicit Off” just if you’re too lazy to say “Dim” — and you’re sure you’re not making ridiculous mistakes about variables.

Apostrophe

In your subroutine, you can type comments to help programmers understand your program. The comments can mention your name, the date you wrote the program, the program’s purpose, the purpose of each variable, special tricks you used, cynical comments, and any other comments you’d like to share with your programming buddies and to remind yourself of how you’ve been thinking.

To type such a comment in your subroutine, begin the comment with an apostrophe, like this:

When you run the program, the computer ignores everything that’s to the right of an apostrophe. So the computer ignores lines 1 and 2; in lines 3 & 4, the computer ignores the “because…”; in the bottom line, the computer ignores the comment about being unhaunted. Since c is 40, and h is 23, the bottom line makes the computer say:

Everything to the right of an apostrophe is called a comment (or remark).

Turning green When you type the subroutine,
the computer makes each apostrophe and comment turn green. Then the computer ignores what’s green.

Temporarily ignore Suppose you’ve written a subroutine but wonder what would happen if one of the lines were deleted. To find out, you could delete the line (by pressing the Delete key repeatedly or using other techniques), then run the shortened program, then put the line back in (by retyping it). But here’s a faster way to do that experiment:

Temporarily deactivating a line (by putting an apostrophe before it so it becomes a comment) is called commenting out the line.

Multiple lines To make several lines become comments, you can type an apostrophe in front of each of those lines; but here’s a faster way: drag across those lines (by using your mouse), then click the Comment-out button (which is near the screen’s top, under “Tools”, and shows two green lines between black lines).

That makes the computer type an apostrophe in front of each of those lines and makes the lines turn green.

Later, when you want to reactivate those lines, drag across them again then click the Uncomment button (which is to the right of the Comment-out button): that removes the apostrophes and makes the lines turn black again.

 

 

 

 

 

You can make the computer show answers in many places. Let’s review the places you saw previously, then explore places that are more exotic.

Top of Form1

You learned that if Form1’s subroutine says —

the computer writes the answer, 7, at the top of Form1, where Form1’s title belongs.

Unfortunately, the top of Form1 doesn’t have much space: the answer must be narrow (unless you widened Form1) and the answer must not consume 2 lines.

Pop-up window

If the subroutine says —

the computer writes the answer in a pop-up window that appears suddenly.

Afterwards, the computer waits for the human to click “OK”.

Middle of Form1

If you’ve created a label (by double-click the Label tool) and your subroutine says —

the computer writes the answer in the middle of Form1, where Label1 is.

Immediate window

If the subroutine says —

the computer writes the answer in the immediate window, which should appear suddenly at your screen’s bottom.

That window also shows any previous chitchat:

After you admire the immediate window, look at Form1.

Then end the program (by clicking Form1’s close button).

Immediate without subroutine You can use the immediate window without writing a subroutine! Here’s how.

Make the immediate window appear (by clicking Debug then Windows then Immediate).

Click in that window and type a line such as —

or, more briefly:

When you finish typing that line (and press the Enter key), the computer will immediately write the answer, 7, in that same window, below your question.

Output window

If the subroutine says —

the computer writes the answer in the output window, which should appear suddenly at your screen’s bottom.

That window also shows any previous output from this run.

After you admire the output window, look at Form1.

Then end the program (by clicking Form1’s close button).

Console screen

To create a new program normally, you click “New Project” then double-click “Windows Forms Application”.

Instead of double-clicking “Windows Forms Application”, try double-clicking “Console Application”. That tells the computer you want a stripped-down version of Visual Basic, where the computer writes answers on a console screen (which looks like DOS instead of Windows and has no forms or buttons or icons).

When you’ve double-clicked the Console Application icon, you immediately see this stripped-down subroutine:

Click in the middle of that subroutine and say “Console.WriteLine(5 + 2)”, so the subroutine becomes this:

Just above the “End Sub”, say “Do” and “Loop”, like this:

When you type the “Do” (and press Enter), the computer automatically types the “Loop” for you.

When you run the program (by pressing F5), the computer writes the answer on a console screen, which is a window whose middle looks like DOS. (To create a 2-line answer, give 2 Console.WriteLine commands. At the end of each answer, the computer presses the Enter key, unless you say Write instead of WriteLine.) Your subroutine’s “Do” and “Loop” make the computer pause, so you have time to read the answer.

After you’ve read the answer, close the console screen (by clicking its X button).

Avoiding Do In the subroutine, instead of typing “Do” (and waiting for the computer to type “Loop”), you can type “Console.ReadKey()”, so the program looks like this:

The “Console.ReadKey()” makes the computer wait for the human to press a key. When the human presses any key (such as Enter), the computer ends the program and closes the console screen.

Print form

Here’s how to let the human print Form1 onto paper.

Double-click the PrintForm tool, which is in the Visual Basic PowerPacks category (whose tools you can see by clicking the triangle left of “Visual Basic PowerPacks” once or twice). That puts a PrintForm1 icon below Form1 and lets subroutines mention “PrintForm1”.

On Form1, create a button (by double-clicking the Button tool). Make the button’s text say “Print” (by clicking “Text” then typing “Print”). Double-click the button, so you can write the button’s subroutine. Make the button’s subroutine say:

When the human runs the program and clicks the Print button, the computer will print most of Form1 onto paper.

The computer doesn’t bother printing Form1’s border or Text (title). It prints just Form1’s middle, including the objects in it.

Hard disk

If Form1’s subroutine says —

the computer writes the number 7 (the answer to 5+2) onto your hard disk, in a file called Joan.txt. Unfortunately, that file is hard to access, since it’s buried in folders. (Specifically, it’s in the Debug folder, which is in the bin folder, which is in your program’s inner folder, which in your program’s outer folder, which is in the Projects folder, which is in the Visual Studio 2010 folder, which is in the Documents folder.)

If you don’t like the name Joan, invent a different name instead.

ProgramData folder This line is more practical:

It makes the computer write the number 7 (the answer to 5 + 2) onto your hard disk, in a file called Joan.txt, which is in the ProgramData folder.

After you’ve run the program (by pressing F5), you can see Joan.txt by doing this:

Documents folder If you want Joan.txt to be in the Documents folder instead of the ProgramData folder, type these lines instead:

The top two lines makes the variable doc stand for the Documents folder. In the bottom line, the doc makes Joan.txt be in the Documents folder.

After you’ve run the program (by pressing F5), you can see Joan.txt by doing this:

Append If Joan.txt exists before you run the subroutine, the subroutine erases that old Joan.txt to create a Joan.txt — unless you change the bottom line’s “False” to “True”, which makes the subroutine append the new answer to the end of the old Joan.txt, to make Joan.txt become longer and include both answers. In the bottom line, “True” means “append to the old file”; “False” means “don’t append to the old file; erase the old file.”

Reading Joan.txt After the computer has put an answer into Joan.txt, you can run a reading program that reads Joan.txt.

If Joan.txt is in the ProgramData folder, the reading program can have Form1’s subroutine say:

That line makes the computer read Joan.txt and tell you what answer Joan.txt contains.

If Joan.txt is in the Documents folder, the reading program can have Form1’s subroutine say:

Those lines make doc be the Documents folder and make Text be the answer that the computer reads from doc’s Joan.txt.

Rich-text box Try this experiment.…

Create a new program. On Form1, put a rich-text box (so the human can type a document into the box) and put a Save button (a button whose title is “Save”).

To make the Save button work properly (so pressing it copies the human’s typing from the box to the hard disk), make the button’s subroutine be this:

The bottom line means: take what’s in the rich-text box and save it as a file; put the file into the Documents folder and call it Joan.doc.

When the human runs that program, the computer will let the human type a document (essay) into the rich-text box. Then computer will wait for the human to click the Save button (which makes the computer copy the document to the hard disk’s Documents folder, in a rich-text file called Joan.doc).

You can see Joan.doc by doing this:

“Save As” dialog box That subroutine forces the document to be in the Documents folder and be called “Joan.doc”. Here’s how to make the subroutine more flexible, (so the human can choose what folder to put the document in and what name to give the document.…

Double-click the SaveFileDialog tool (which is in the Dialogs category). That creates a SaveFileDialog1 icon below Form1.

In the SaveFileDialog1’s property list, click “DefaultExt” and type “doc”. That will secretly put “.doc” at the end of every filename.

Make the Save button’s subroutine be this:

When the human clicks the Save button, the subroutine’s top line makes the computer show the “Save As” dialog box, which lets the human invent a file name and choose a folder to put it in. For example, if the human types “Joe” (and then presses the Enter key), the file will be called “Joe.doc” (because the SaveFileDialog1’s property list said the default extension is “doc”).

The subroutine’s bottom line means: look at the document that was typed in RichTextBox1, and save it as a file on the hard disk, using the file name (and folder) that the human specified in the “Save As” dialog box.

Say “document” Since RichTextBox1’s main purpose is to handle a document, programmers prefer to say just “document” instead of “RichTextBox1” and write the Save button’s program this way:

To do that, you must change the box’s name from “RichTextBox1” to “document”. Here’s how:

Reading Joan.doc After the computer has saved (copied) a document into your hard disk’s Joan.doc, you can run a reading program that reads Joan.doc.

The reading program should have a rich text box named “document”. It should also have an “Open” button whose subroutine says:

But to make the computer understand what “OpenFileDialog1” means, you must double-click the OpenFileDialog tool before typing that subroutine.

You can create a menu.

Menu bar

At the top of Form1, let’s create this menu bar:

Let’s program the computer so clicking “Love” makes the computer say “I love you”, and clicking “Hate” makes the computer say “I hate being a computer”.

Here’s how to accomplish all that.…

Double-click the MenuStrip tool (which is in the “Menus & Toolbars” category).

Click “Type Here” (which is near Form1’s top). Then you see a blank box (plus two “Type Here” boxes). In the blank box, type your menu’s first word (“Love”).

Click the box that’s to the right of “Love”. Type your menu’s second word (“Hate”).

Congratulations! You created a menu!

Create menu subroutines Double-click “Love”, then write this subroutine telling the computer what to do if “Love” is clicked:

(The computer already typed the top and bottom lines for you, so type just the middle line.) When you finish typing that line, click the “Form1.vb [Design]” tab.

Double-click “Hate”, then write this subroutine about clicking “Hate”:

Run the program Go ahead: run the program (by pressing the F5 key). You see the menu bar you created:

Clicking “Love” makes the computer say “I love you”; clicking “Hate” makes the computer say “I hate being a computer”.

Pull-down menu

Let’s expand the menu by adding “Color”, so the menu becomes this:

Let’s program the computer so clicking “Color” makes this pull-down menu appear under Color:

Let’s program so clicking one of those colors makes Form1’s background be that color.

Here’s how to accomplish all that.…

Create a new menu item If your program is still running, stop it (by clicking its X button). Look at Form1’s design (by clicking the “Form1.vb [Design]” tab). Click the “Type Here” that’s to the right of “Hate”. In the blank box that appears, type your menu’s third word (“Color”).

Create a pull-down menu To create Color’s pull-down menu (saying “Yellow” and “Red”), click the “Type Here” that’s under “Color”. In the blank box that appears, type “Yellow”. In the box under “Yellow”, type “Red”.

Congratulations! You created a pull-down menu!

Create menu subroutines Double-click “Yellow”, then write this subroutine about Yellow:

Click the “Form1.vb [Design]” tab, then double-click “Red”, then write this subroutine about Red:

Run the program Go ahead: run the program (by pressing the F5 key). You see the menu bar you created:

Clicking “Color” makes the computer show Color’s pull-down menu; clicking the “Yellow” or “Red” makes Form1’s background turn that color.

Submenu

Let’s expand Color’s pull-down menu by adding “Blue”, so the menu becomes this:

Let’s program the computer so clicking “Blue” makes this submenu appear to the right of Blue:

Let’s program so clicking one of those kinds of blue makes Form1’s background be that color.

Here’s how to accomplish all that.…

Create a new menu item If your program is still running, stop it (by clicking its X button). Look at Form1’s design (by clicking the “Form1.vb [Design]” tab). Click “Color” then the “Type Here” that’s under “Red”. In the blank box that appears, type pull-down menu’s third word (“Blue”).

Create a submenu To create Blue’s submenu (saying “Light Blue” and “Dark Blue”), click the “Type Here” that’s to the right of “Blue”. In the blank box that appears, type “Light Blue”. In the box under “Light Blue”, type “Dark Blue”.

Congratulations! You created a submenu!

Creating a submenu for Blue made a right-arrow appear next to “Blue”, so Color’s pull-down menu looks like this:

That right-arrow means “has a submenu”.

Create subroutines Double-click “Light Blue”, then write this subroutine about Light Blue:

Click the “Form1.vb [Design]” tab, then double-click “Dark Blue”, then write this subroutine about Dark Blue:

Run the program Go ahead: run the program (by pressing the F5 key). You see the menu bar you created:

Clicking “Color” makes the computer show Color’s pull-down menu; clicking “Blue” makes the computer show Blue’s submenu; then clicking “Light Blue” or “Dark Blue” makes Form1’s background turn that color.

Rearranging menu items

After you’ve created a menu, you can rearrange its items. Here’s how.…

If your program is still running, stop it (by clicking its X button). Look at Form1’s design (by clicking the “Form1.vb [Design]” tab).

To delete an item, click it then press the Delete key. If you change your mind, click the Undo button (which shows a blue arrow bending toward the left).

 To move an item that’s on the menu bar (“Love”, “Hate”, or “Color”), drag that item across to where you want it — and, to make sure the computer doesn’t ignore you, drag slightly farther. To move an item that’s on a pull-down menu (“Yellow”, “Red”, or “Blue”) or submenu (“Light Blue” or “Dark Blue”), drag the item up or down to where you want it — and to make sure the computer doesn’t ignore you, drag slightly farther.

Here’s how to invent a minimalist word-processing program.

Big Form1

Create a new program. Widen Form 1 (by dragging its bottom-right corner toward the right).

Tool strip

Onto Form 1, put a tool strip (toolbar) by doing this:

Rich text box

Onto Form1, put a rich text box (by double-clicking the RichTextBox tool). Give that box the desired properties by doing this:

More tools

Double-click these tools, which you’ll need to finish the program:

Then icons for those tools appear below Form1.

Subroutines

For each button on the tool strip, write a subroutine. Here’s how.…

Double-click the tool strip’s first button (the New button, which looks like a blank sheet of paper with a folded corner). Type this line (for the New button’s subroutine):

Make Form1 appear again (by clicking the “Form1.vb [Design]” tab). Double-click the tool strip’s next button (the Open button, which looks like a yellow manila folder that’s opening). Type these lines (for the Open button’s subroutine):

Make Form1 appear again (by clicking the “Form1vb [Design]” tab). In similar fashion, type these lines for the Save button:

Type this line for the Print button:

Type this line for the Cut button:

Type this line for the Copy button:

Type this line for the Paste button:

Type this line for the Help button:

Run

When you run the program (by pressing F5), the program works correctly, if you did what I said!

Congratulations on creating a word-processing program.

The program’s main limitations are:

Surpassing those limitations would require subroutines that are much longer!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Here’s how to make the computer repeat.

Do…Loop

The computer can be religious. Just make Form1’s subroutine say this:

When you run the program, the computer shows a message box saying “I worship your feet” and waits for the human to click OK. Then the computer shows a message box saying “But please wash them” (and waits for the human to click OK again).

To make the computer do the lines many times, say “Do” above the lines and say “Loop” below them, so the subroutine looks like this:

The lines being repeated (the MsgBox lines) should be between the words Do and Loop and indented. (After you’ve typed the word “Do” and pressed Enter, the computer will automatically type the word “Loop” and created an indented blank space for you to type in.)

Run the program (by pressing the F5 key). The computer says “I worship your feet” (and waits for the human to click OK), then says “But please wash them” (and waits for OK), then goes back and says “I worship your feet” again (and waits for OK), then says “But please wash them” again (and waits for OK), then goes back and says the same stuff again, and again, and again, and again, forever.

Since the computer’s thinking keeps circling back to the same lines, the computer is said to be in a loop. In that subroutine, the Do means “do what’s underneath and indented”; the Loop means “loop back and do it again”. The lines that say Do and Loop — and the lines between them — form a loop, which is called a Do loop.

The computer does that loop repeatedly, forever — or until you abort the program by doing this:

That works just if you’re in the Visual Basic environment (so you see the Stop Debugging button). If you’re not in the Visual Basic environment (because you’re running the .exe file directly), the only way to abort a looping program is to shut down the computer (click the Start button then, in Windows 7, click Shutdown) or try this:

In that program, since the computer tries to go round and round the loop forever, the loop is called infinite. The only way to stop an infinite loop is to abort it.

Disappearing-message-box bug

When running a loop, the computer might accidentally
lose the program’s focus and forget to show the message box. To make the message box reappear, click the message box’s button, which is on the taskbar. (The taskbar is at the screen’s bottom and runs from the Start button to the clock.) Try double-clicking the message box’s button. To run the program again, try clicking the green right-arrow (instead of pressing the F5 key).

GoTo

Instead of typing —

you can type:

(When you type that subroutine, the computer automatically spaces it correctly: when you press Enter at the top line’s end, the computer automatically unindents “joe:”.) The top line (named joe) makes the computer say “I worship your feet”. The next line makes the computer say “But please wash them”. The bottom line makes the computer Go back To the line named joe, so the computer forms a loop. The computer will loop forever — or until you abort the program (by clicking the Stop Debugging button, twice).

You can give a line a short name (such as joe) or a long name (such as BeginningOfMyFavoriteLoop). The name can even be a number (such as 10). Put the name at the line’s beginning. After the name, put a colon (the symbol “:”).

The line’s name (such as joe or BeginningOfMyFavoriteLoop or 10) is called the line’s label.

Skip ahead This subroutine is insulting:

Let’s turn that insult into a compliment. To do that, insert the shaded items:

The computer begins by saying “Your face is outstanding.” Then the computer does GoTo conclusion, which makes the computer Go skip down To the conclusion line, which says “It deserves an award!” So the subroutine makes the computer say just —

and:

Is GoTo too powerful? Saying GoTo gives you great power: if you make the computer GoTo an earlier line, you’ll create a loop; if you make the computer GoTo a later line, the computer will skip over several lines of your subroutine.

Since saying GoTo is so powerful, programmers are afraid to say it. Programmers know that the slightest error in saying GoTo will make a program act very bizarre! Programmers feel more comfortable using milder words instead (such as Do…Loop), which are safer and rarely get botched up. Since saying GoTo is scary, many computer teachers prohibit students from using it, and many companies fire programmers who say GoTo instead of Do…Loop.

But saying GoTo is fine when you’ve learned how to control the power! Though I usually say Do…Loop instead of GoTo, I say GoTo in certain situations where saying Do…Loop would be awkward.

Exiting a Do loop

Let’s create a guessing game, where the human tries to guess the computer’s favorite color, which is pink. To do that, say GoTo or Exit Do or Loop Until. Here’s how.…

GoTo Just make Form1’s subroutine say this:

The top line (which is called AskTheHuman) asks the human to guess the computer’s favorite color.

If the guess is “pink”, the computer says:

But if the guess is not pink, the computer will instead say “No, that’s not my favorite color” and then Go back To AskTheHuman again to guess the computer’s favorite color.

Exit Do Here’s how to write that subroutine without saying GoTo:

The Do loop makes the computer do this repeatedly: ask “What’s my favorite color?” and then say “No, that’s not my favorite color.”

The only way to stop the loop nicely (without abortion) is to guess “pink”, which makes the computer Exit from the Do loop; then the computer proceeds to the line underneath the Do loop. That line makes the computer say:

Loop Until Here’s another way to program the guessing game:

The Do loop makes the computer do this repeatedly: say “You haven’t guessed my favorite color yet!” and then ask “What’s my favorite color?”

The Loop line makes the computer repeat the indented lines again and again, until the guess is “pink”. When the guess is “pink”, the computer proceeds to the line underneath the Loop and prints “Congratulations!”

The Loop Until’s condition (guess = “pink”) is called the loop’s goal. The computer does the loop repeatedly, until the loop’s goal is achieved. Here’s how:

Saying —

is just a briefer way of saying this pair of lines:

For…Next

Let’s make the computer say these sentences:

To do that, put these lines into Form1’s subroutine:

The top line (For x = 1 To 5) says that x will be every number from 1 to 5; so x will be 1, then 2, then 3, then 4, then 5. The line underneath (which the computer indents) says what to do about each x: it says to create a message box saying “I like the number ” and x.

Whenever a subroutine says the word For, it must also say Next; so the bottom line says Next. The computer types the word “Next” for you automatically.

The indented line, which is between the For line and the Next line, is the line that the computer will do repeatedly; so the computer will repeatedly say “I like the number ” and an x. The first time, the x will be 1, so the computer will say:

The next time, the x will be 2, so the computer will say:

The computer will say similar sentences, for every number from 1 up to 5.

Monster song Let’s make the computer say these lyrics:

To do that, type these lines —

and make x be every number from 2 up to 4:

At the end of the song, say the closing line:

That program makes the computer print the entire song.

Here’s an analysis:

Since the computer does the indented lines repeatedly, those lines form a loop. Here’s the general rule: the statements between For and Next form a loop. The computer goes round and round the loop, for x=2, x=3, x=4, and x=5. Altogether, it goes around the loop 4 times, which is a finite number. Therefore, the loop is finite.

If you don’t like the letter x, choose a different letter. For example, you can choose the letter i:

When using the word For, most programmers prefer the letter i; most programmers say “For i” instead of “For x”. Saying “For i” is a tradition. Following that tradition, the rest of this book says “For i” (instead of “For x”), except in situations where some other letter feels more natural.

Say the squares To find the square of a number, multiply the number by itself. For example, the square of 3 is “3 times 3”, which is 9. The square of 4 is “4 times 4”, which is 16.

Let’s make the computer say the square of 3, 4, 5, etc., up to 10, like this:

To do that, type this line —

and make i be every number from 3 up to 10, like this:

Count how many copies This program makes the computer say “I love you” 4 times:

Here’s a smarter program, which asks how many times you want the computer to say “I love you”:

When you run that program, the computer asks:

If you answer 5 (and click the OK button), the n becomes 5 (so the computer says “I love you” 5 times). If you answer 7 instead, the computer says “I love you” 7 times. Get as much love as you like!

That program illustrates this rule:

Step The For statement can be varied:

To count down, you must use the word Step. To count from 17 down to 5, give this instruction:

This program prints a rocket countdown:

The computer will say:

This statement is tricky:

It says to start i at 5, and keep adding 3 until it gets past 16. So i will be 5, then 8, then 11, then 14. The i won’t be 17, since 17 is past 16. The first value of i is 5; the last value is 14.

In the statement For i = 5 To 16 Step 3, the first value or initial value of i is 5, the limit value is 16, and the step size or increment is 3. The i is called the counter or index or loop-control variable. Although the limit value is 16, the last value or terminal value is 14.

Programmers usually say “For i”, instead of “For x”, because the letter i reminds them of the word index.

The computer can do fancy calculations.

Exponents

In Form1’s subroutine, try giving this command:

To type the symbol ^, do this: while holding down the Shift key, tap this key:

^ 6

That symbol (^) is called a caret.

In that line, the “4 ^ 3” makes the computer use the number 4, three times. The computer will multiply together those three 4’s, like this: 4 times 4 times 4. Since “4 times 4 times 4” is 64, the computer will say:

In the expression “4 ^ 3”, the 4 is called the base; the 3 is called the exponent or power.

Here’s another example:

The “10 ^ 6” makes the computer use the number 10, six times. The computer will multiply together those six 10’s (like this: 10 times 10 times 10 times 10 times 10 times 10) and say the answer, 1000000.

Here’s another example:

The “3 ^ 2” makes the computer use the number 3, two times. The computer will multiply together those two 3’s (like this:
3 times 3) and say the answer, 9.

Order of operations The symbols +, -, *, /, and ^ are all called operations.

To solve a problem, the computer uses the three-step process taught in algebra (and pre-algebra). For example, suppose you say:

The computer will not begin by subtracting 3 from 70; instead, it will use the three-step process:

In each step, it looks from left to right. For example, in step 2, it sees / and gets rid of it before it sees *.

Speed Though exponents are fun, the computer handles them slowly. For example, the computer handles 3 ^ 2 slower than 3 * 3. So for fast calculations, say 3 * 3 instead of 3 ^ 2.

Square roots What positive number, when multiplied by itself, gives 9? The answer is 3, because 3 times itself is 9.

3 squared is 9. 3 is called the square root of 9.

To make the computer deduce the square root of 9, type this:

The computer will print 3.

The symbol Math.Sqrt is called a function. The number in parentheses (9) is called the function’s input (or argument or parameter). The answer, which is 3, is called the function’s output (or value).

Math.Sqrt(9) gives the same answer as 9 ^ .5. The computer handles Math.Sqrt(9) faster than 9 ^ .5.

Cube roots What number, when multiplied by itself and then multiplied by itself again, gives 64? The answer is 4, because 4 times 4 times 4 is 64. The answer (4) is called the cube root of 64.

Here’s how to make the computer find the cube root of 64:

The computer will say 4.

Stripping

 Sometimes the computer prints too much info: you wish the computer would print less, to save yourself the agony of reading excess info irrelevant to your needs. Whenever the computer prints too much info about a numerical answer, use Math.Abs, Fix, Int, Math.Ceiling, Math.Round, or Math.Sign.

Math.Abs, Fix, Int, Math.Ceiling, Math.Round, and Math.Sign are all called stripping functions or strippers or diet functions or diet pills, because they strip away the number’s excess fat and reveal just the fundamentals that interest you.

Pi

A circle’s circumference (the distance around a circle) is about 3 times as long as the circle’s diameter (the distance across the circle). So the circumference divided by the diameter is about 3. More precisely, it’s pi, which is about 3.1415926535897931, a number that Visual Basic calls Math.PI. If you type —

the computer will display this approximation:

Avoid “Math.”

Many of those functions expect you to type “Math.” To avoid having to type “Math.”, put this line at your program’s top (above “Public Class Form1”):

Then you can omit “Math.” For example, instead of typing —

you can type just:

Instead of typing —

you can type just:

If you want x to be a variable in your subroutine, you must warn the computer by giving your subroutine a command such as:

Here’s how to make your program run faster, consume less RAM, and correct more errors: instead of saying just “Dim x”, warn the computer what type of data the x will stand for, by giving one of these 8 popular commands:

Some of those commands are used rarely. These 8 commands are the most popular:

Here’s how to choose among them:

For example, if you want x to be 3000000, say:

According to the chart’s top line, saying “Dim x As Integer” makes x consume 4 bytes of RAM. The computer can store 3000000 (or any integer up to 2147483647) in just 4 bytes of RAM, because the computer stores the number by using a special trick called binary representation.

These 7 variations are less popular:

Details

Here are more details about the 8 popular Dim commands.

Integer An Integer is a number from 0 to 2147483647, with maybe a negative sign in front, but without a decimal point. For example, these numbers can all be Integer:

Technical note: although 2147483648 is slightly too big to be an Integer, -2147483648 is a special number that can be an Integer, though it’s rarely used and must be written as:

If you say “Dim x As Integer” and then try to say “x = 52.9”, the computer will round 52.9 to 53, so x will be 53.

To round, Visual Basic 2010 makes the computer use this strange method, called unbiased rounding:

That makes .5 sometimes round down and sometimes rounds up, so there’s no bias toward rounding in a particular direction. That unbiased rounding method appeals to statisticians (and a few economists and very few bankers) who want to eliminate bias from rounded results. It’s called unbiased rounding (or round-to-even or statisticians rounding or bankers rounding or Dutch rounding or Gaussian rounding).

Long A Long is a number from 0 to 9223372036854775807, with maybe a negative sign in front, but without a decimal point. For example, these numbers can all be Longs:

Technical note: although 9223372036854775808 is slightly too big to be a Long, -9223372036854775808 is a special number that can be a Long, though it’s rarely used and must be written as:

If you say “Dim x As Long” and then try to say “x = 52.9”, the computer will round 52.9 to 53, so x will be 53. (To round, the computer uses unbiased rounding.)

If you write a number that has no decimal point and is small (no more than 2147483647), the computer assumes you want it to be an Integer. If you want it to be a Long instead, put L after it, like this: 57L. For example, if you tell the computer to multiply 3000 by 1000000, like this —

the computer assumes you want to multiply the Integer 3000 by the Integer 1000000; but the answer is too long to be an Integer, so the computer gripes (by saying “not representable in type ‘Integer’”). Multiplying 3000 by 1000000 is okay if you say the numbers are Longs, not Integers, like this:

Then the computer will show the correct answer:

Double A Double is a number from 0 to 1E308 (which is a “1 followed by 308 zeros”), with maybe a negative sign and a decimal point. After the decimal point, you can have as many digits as you wish. For example, these numbers can all be Double:

The computer manages to store a Double rather briefly (just 8 bytes) by “cheating”: the computer stores the number just approximately, to an accuracy of about 15 significant digits.

For example, if you say —

the computer will show 15 digits:

If you say —

the computer will round to 15 digits and show:

When handling Double variables, the computer can give inaccurate results. The inaccuracy is especially noticeable if you do a subtraction where the two numbers nearly equal each other. For example, if you say —

the computer will make x be approximately 8000.1, so y will be approximately .1. The Print line will print:

Notice that the last few digits are wrong! That’s the drawback of Double: you can’t trust the last few digits of the answer! Double is accurate enough for most scientists, engineers, and statisticians, since they realize all measurements of the real world are just approximations; but Double is not good enough for accountants who fret over every penny. Double’s errors drive accountants bananas. For accounting problems that involve decimals, consider using Decimal instead of Double, since Decimal is always accurate, though slower.

Technical notes:

Decimal If you say “Dim x as Decimal” (instead of “Dim x as Double”, the computer will store x very accurately (28 digits, and sometimes a 29^th). The computer handles Decimals slower than any other kind of number, so say “Dim x as Decimal” just if you need extra accuracy and don’t care about speed.

If you say “Dim x as Decimal”, the computer actually stores all x’s digits as an extra-long integer and also stores a note about where the decimal point belongs.

To write a Decimal number, put D after the number, to emphasize that the number is a Decimal, not a Double, like this:

The biggest permissible Decimal is 79228162514264337593543950335D (which has 29 digits and no decimal point). The tiniest permissible Decimal is 0.0000000000000000000000000001D (which has 27 zeros after the decimal point).

A Decimal number cannot contain E. It’s limited to 28 (or 29) digits. When counting how many digits are in the number, you must count the zeros: the limit is indeed 28 (or 29) digits (not 28 “significant digits”).

Date A Date is a date with time. For example, these lines make x be December 31, 2009, at 30 seconds after 11:59 PM:

Notice you must put the symbol # before and after the date-with-time. The computer will print:

For the year, you can pick 2009 or 1999 or 1776 or 1492 or even earlier. You can pick any year from 1 (which was shortly after Christ) to 9999 (which is many centuries from now). If you type a 2-digit year, the computer will put “20” before your typing, to make a 4-digit year (unless your 2-digit year is at least 30, in which case the computer will put “19” before your typing instead).

You can omit any part of the date-and-time that doesn’t interest you. For example, if you don’t care about the seconds, leave them out. If you don’t care about the time-of-day, leave it out and type just the date; if you don’t care about the date, leave it out and type just the time of day.

The computer makes assumptions:

To avoid pissing off people who don’t like those assumptions, the computer avoids displaying 12:00:00 AM and avoids displaying 1/1/1. For example, if you leave out the time of day and type this —

x will be #12/31/2009 12:00:00 AM# but the computer will display just:

If you leave out the date and type this —

x will be #1/1/1 11:59:30 PM# but the computer will display just:

If you say —

the computer will make x be the current date-with-time. For example, if the computer encounters that line while running the program on December 31, 2009 (at 30.16 seconds after 11:59 PM), x will become #12/31/2009 11:59:30 PM#.

Boolean A Boolean is either the word True or the word False. Here’s an example:

The computer will display:

Here’s another example:

The computer will display:

Technical notes:

String A String is a collection of characters, such as “joy” or “I love you” or “aieee luf ya” or “76 trombones” or “GO AWAY!!!” or “xypw exr///746”. Here’s an example:

The computer will display:

Versions of Visual Basic before 2005 used a code called the American Standard Code for Information Interchange (Ascii), which consumed just 1 byte per character; but Visual Basic 2005 & 2008 & 2010 use a different code instead, called Unicode, which uses 2 bytes per character, to permit fancier characters for foreign languages.

Since the string “joy” contains 3 characters, and each character consumes 2 bytes, x consumes 6 bytes of RAM — plus 10 bytes to remember how long the string is. So altogether, x consumes 16 bytes of RAM.

If you say “Dim x As String” and try to say “x = 9 + 3.5”, the computer will look at the equation’s right side, realize it’s 12.5, and try to make x be 12.5; but because of the “Dim x as String”, the computer must but must turn x into a string, so x will become the string “12.5” (which is four characters long).

Character A Char is a single character, such as “j”. It consumes just 2 bytes. To emphasize that “j” is just a single character, not “a string whose length is 1”, write c after the “j”, like this:

The computer will display:

So if x is a Char, the computer requires just 2 bytes to store it. (To store a String, the computer needs 2 bytes per character, plus 10 bytes to store the string’s length; but to store a Char, the computer needs just 2 bytes, since the computer doesn’t have to store a length.)

If you say —

the x will be just the first character of the string “hat”, so x will be just “h”. Then if you say —

the computer will display just:

Object You’ve learned that x can stand for a number, date, Boolean, string, or character.

Here’s another possibility: x can stand for an object, such as Form1 or Button1 or any other VB thing, such as Color.Red.

For example, suppose you created a button called Button1. If you put this line in Form1’s subroutine, Button1’s title will become “Click me”:

These lines do the same thing:

Saying “Dim x As Object” is vague. It has exactly the same meaning as “Dim x”, which is vague. If you say “Dim x As Object” (or just “Dim x”), you’re saying that x stands for a Windows object (such as Form1 or Button1) or some other kind of object (such as a number, date, Boolean, string, or character). The computer handles such an x slowly: it consumes 4 bytes to remember what part of the RAM holds x’s details, plus several bytes to store the details.

Multiple variables

If you want x and y to be Integers, z to be a String, and temperature to be a Double, say this —

or say it all in one line:

Suffix

Here’s the normal way to make x be a String:

This way is shorter:

That dollar sign means “As String”. The dollar sign is called a suffix (or type-declaration character).

You can use these suffixes:

Repeating the suffix Below the Dim line, you can type the suffix again if you wish. For example, after you’ve made x be a string by saying —

you can say either —

or this, which means the same thing:

The computer doesn’t care whether you type the $ again. Type it just if you want to emphasize it to other programmers who look at your subroutine.

Constants

Your subroutine can mention variables (such as x and y) and constants (such as 3.7 and “I love you”). Here’s how the computer tells a constant’s type:

VarType

Each type of constant has a code number:

If you say VarType, the computer will examine a constant and tell you its code number. For example, if you say —

the computer will examine 4.95D, realize it’s a Decimal, and say Decimal’s code number, which is:

Here are more examples:

VarType of a variable If you say VarType(x), the computer will notice what type of variable x is and print its code number. For example, if you say —

the computer will say Decimal’s code number, which is 14.

If you say just “Dim x” (or “Dim x As Object”) without specifying further details of x’s type, VarType(x) will be whatever type the x acquires. For example, if you say —

the computer will print Decimal’s code number, which is 14.

TypeName

If you say TypeName instead of VarType, the computer will say the type’s name instead of its code number.

For example, if you say —

the computer will say:

Instead of saying “Object” (or “Nothing”), the computer will try to be more specific. For example, if you created a command button called Button1 and say —

the computer will say:

If x is an Object but doesn’t have a more specific value or type yet, “Text = TypeName(x)” will make the computer say:

Initial value

Instead of saying —

you can combine those two lines into this single line:

In that line, 7 is called x’s initial value (or initializer), because it’s what x is initially (in the beginning).

You can shorten that line further, by saying just this:

Since 7 is an Integer (according to the rules about which constants are Integers), the computer will assume you also mean “x As Integer”. If you say this instead —

the computer will assume you mean “x As Double”.

Saying “Dim x = 5” has a slightly different effect than saying “Dim x” then “x = 5”.Compare these subroutines:

In the left subroutine, the Dim line says x is a vague variable (an object). The next line says x is 5. The next line changes x to 8.4, so Text will be 8.4. In the right-hand subroutine, the first line says x is 5 but also makes x be an integer variable (since that line implies “x As Integer”); since x is an integer variable, the next line makes x be 8 (not 8.4), so Text will be just 8.

Operations

When you do operations (add, subtract, multiply, divide, exponents, or beyond), here’s what kind of answer you get.

Exponents When you do exponents (using the symbol “^”), the answer is a Double.

Division When you divide one number by another (using the symbol “/”), here’s what happens:

Add, subtract, multiply When you add, subtract, or multiply numbers (using the symbol + or - or *), here’s what happens:

Advanced math Here’s how the computer handles advanced math:

Combine When you combine strings or numbers (by using the symbol “&”), the answer is a string.

Form1 declarations

Normally, each subroutine has its own variables. For example, if Form1’s subroutine uses a variable called x, and Button1’s subroutine uses a variable that’s also called x, Form1’s x has nothing to do with Button1’s x. Form1’s x is stored in a different part of RAM from Button1’s x. If Form1 says x = 5, Button1’s x remains unaffected by that statement.

If you want Form1’s x to be the same as Button1’s x and use the same RAM, say “Dim x” above the “Private Sub Form1” line instead of below.

Example For example, try this experiment.…

Create a new program. Double-click Form1, so you can type Form1’s subroutine. Your screen looks like this:

Click above the “Private Sub Form1” line and type “Dim x” there, so your screen looks like this:

Type Form1’s subroutine under the “Private Sub Form1” line, like this:

Create Button1 (by clicking the “Form1.vb [Design]” tab then double-clicking the Button tool). Double-click Button1, then type “Text = x” for Button1’s subroutine. Altogether, your screen looks like this:

Since the “Dim x” is above both subroutines (instead of being buried inside one subroutine), the x’s value affects both subroutines (not just one of them).

When you run that program (by pressing F5), Form1’s subroutine makes x be 5. Then when you click Button1, Button1’s subroutine makes Text be x, which is 5, so the computer says:

Conversion functions

In the middle of a calculation, you can convert to a different type of data by using these conversion functions:

For example, CInt(3.9) is “3.9 converted to the nearest Integer”, which is 4. If you say —

the computer will say:

If you say —

the computer will say:

Arrays

Instead of being just a number, x can be a list of numbers.

Example For example, if you want x to be this list of numbers —

type this in Form1’s subroutine:

In that line, the symbol “x()” means “x’s list”. Notice that when you type the list of numbers, you must put commas between the numbers and put the entire list of numbers in braces, {}. On your keyboard, the “{” symbol is to the right of the P key and requires you to hold down the Shift key.

Since all numbers in that list are Integers, you can improve that line by saying “As Integer”, like this:

If you don’t say “As Integer”, the computer will treat those numbers as just vague objects, and the program will run slower.

In x’s list, the starting number (which is 81) is called x₀ (which is pronounced “x subscripted by zero” or “x sub 0” or just “x 0”). The next number (which is 52) is called x₁ (which is pronounced “x subscripted by one” or “x sub 1” or just “x 1”). The next number is called x₂. Then comes x₃. So the four numbers in the list are called x₀, x₁, x₂, and x₃.

To make the computer say what x₂ is, type this line:

That line makes Text be x₂, which is 207, so the computer will say:

Altogether, the subroutine says:

The first line says x’s list is these Integers: 81, 52, 207, and 19. The bottom line makes the computer say x₂’s number, which is 207.

This subroutine makes the computer say x₂’s number (which is 207) in a message box:

This subroutine makes the computer say all 4 numbers:

That makes the computer say the numbers for x(1), x(2), x(3), and x(4), so the computer will say 81, 52, 207, and 19.

Here’s a shorter way to make the computer say all 4 numbers:

That makes x’s list be {81, 52, 207, 19}, makes i be
Each number In x (so i is 81, then 52, then 207, then 19), and makes the computer say each i.

Longer lists Instead of having just 4 numbers in the list, you can have 5 numbers, or 6 numbers, or a thousand numbers, or many billions of numbers. The list can be quite long! Your only limit is how much RAM your computer has.

Jargon Notice this jargon:

Different types Instead of having Integers, you can have different types. For example, you can say:

You can even say:

You can even have mixed types:

Uninitialized Instead of making the Dim line include a list of numbers, you can type the numbers underneath, if you warn the computer how many numbers will be in the list, like this:

The top line says x₀, x₁, and x₂ will be Doubles. The next lines say x₀ is 200.1, x₁ is 700.4, and x₂ is 53.2. The bottom line makes the computer say their sum:

In that top line, if you omit the “As Double”, the program will give the same answer but slower. But in that top line, the 2 is required, to warn the computer how many subscripts to reserve RAM for; if you omit the 2 (or type a lower number instead), the computer will gripe.

Usually, the computer is predictable: it does exactly what you say. But sometimes, you want the computer to be unpredictable.

For example, if you’re going to play a game of cards with the computer and tell the computer to deal, you want the cards dealt to be unpredictable. If the cards were predictable — if you could figure out exactly which cards you and the computer would be dealt — the game would be boring.

In many other games too, you want the computer to be unpredictable, to “surprise” you. Without an element of surprise, the game would be boring.

Being unpredictable increases the pleasure you derive from games — and from art. To make the computer act artistic, and create a new original masterpiece that’s a “work of art”, you need a way to make the computer get a “flash of inspiration”. Flashes of inspiration aren’t predictable: they’re surprises.

Here’s how to make the computer act unpredictably.…

Rnd is a RaNDom decimal (bigger than 0 and less than 1) whose data type is Single. For example, it might be .6273649 or .9241587 or .2632801. Every time your program mentions Rnd, the computer concocts another decimal. For example, if Form1’s subroutine says —

the computer says these decimals:

The first time your program mentions Rnd, the computer chooses its favorite decimal, which is .7055475. Each succeeding time your program mentions Rnd, the computer uses the previous decimal to concoct a new one. It uses .7055475 to concoct .533424, which it uses to concoct .5795186. The process by which the computer concocts each new decimal from the previous one is weird enough so we humans cannot detect any pattern.

These lines make the computer say 16 decimals:

You can say either Rnd or Rnd(); the computer doesn’t care. If you say just Rnd, the computer might change it to Rnd().

Percentages

When the computer says random decimals, about half the decimals will be less than .5, and about half will be more than .5.

Most of the decimals will be less than .9. In fact, about 90% will be.

About 36% of the decimals will be less than .36; 59% will be less than .59; 99% will be less than .99; 2% will be less than .02; a quarter of them will be less than .25; etc.

You might see some decimal twice, though most of the decimals will be different from each other.

Randomize

If you run a program about Rnd again, you’ll see exactly the same decimals again, in the same order.

If you’d rather see a different list of decimals, say Randomize() at the subroutine’s top:

When the computer sees Randomize(), the computer looks at the clock and manipulates the time’s digits to produce the first value of Rnd.

So the first value of Rnd will be a number that depends on the time of day, instead of the usual .7055475. Since the first value of Rnd will be different than usual, so will the second, and so will the rest of the list.

Every time you run the program, the clock will be different, so the first value of Rnd will be different, so the whole list will be different — unless you run the program at exactly the same time the next day, when the clock is the same. But since the clock is accurate to a tiny fraction of a second, the chance of hitting the same time is extremely unlikely.

Coin flipping

Here’s how to make the computer flip a coin:

The Randomize line makes the value of Rnd depend on the click. The If line says there’s a 50% chance that the computer will print “heads”; if the computer does not print “heads”, it will print “tails”.

When you’ve typed that subroutine, the computer changes Rnd to Rnd(), so it looks like this:

Until you run the program, you won’t know which way the coin will flip; the choice is random. Each time you run the program, the computer will flip the coin again; each time, the outcome is unpredictable. Try running it several times!

To write that subroutine shorter, say IIf:

The bottom line creates a message box saying this: if the random number is less than .5, then “heads”, else “tails”.

This subroutine flips the coin 10 times:

Love or hate?

Who loves ya, baby? These lines try to answer that question:

The Randomize() line makes the value of Rnd depend on the clock. The Dim line says x will be a variable that stands for a String. The InputBox line makes the computer wait for the human to type a name. Suppose he types Suzy. Then x is “Suzy”. The If line says there’s a 67% chance the computer will say “Suzy loves you, too”, but there’s a 33% chance the computer will instead say “Suzy hates your guts”.

Try running the program several times. Each time, input a different person’s name. Find out which people love you and which people hate your guts — according to the computer!

Here’s a shorter way to write that subroutine:

The Randomize() line makes the value of Rnd depend on the clock. The Dim line makes the variable x be the response to “Type the name of someone you love”. The MsgBox line creates a message box that says x then this: if the random number is less than .67 then “ loves you, too” else “ hates your guts”.

Random integers

If you want a random integer from 1 to 10, ask for 1 + Int(Rnd * 10). Here’s why:

Guessing game These lines play a guessing game:

The second line makes the computer say “I’m thinking of a number from 1 to 10.” The next line makes the computer think of a random number from 1 to 10. The InputBox line asks the human to guess the number.

If the guess is less than the computer’s number, the first If line makes the computer say “Your guess is too low” and then GoTo AskHuman, which lets the human guess again. If the guess is greater than the computer’s number, the second If line makes the computer say “Your guess is too high” and then GoTo AskHuman.

When the human guesses correctly, the computer arrives at the bottom line, which makes the computer say:

Dice These lines make the computer roll a pair of dice:

The second line makes the computer say:

Each of the dice has 6 sides. The next line, Dim a = 1 + Int(Rnd * 6), rolls one of the dice, by picking a number from 1 to 6. The line saying “b = 1 + Int(Rnd * 6)” rolls the other. The bottom line says the total.

For example, a run might say these sentences:

Here’s another run:

Daily horoscope These lines predict what will happen to you today:

The Dim line makes x be a list of 5 fortunes, so x₀ is “wonderful”, x₁ is “fairly good”, x₂ is “so-so”, x₃ is “fairly bad”, and x₄ is “terrible”. Since Int(Rnd * 5) is a random integer from 0 to 4, the x(Int(Rnd * 5)) is a randomly chosen fortune. The computer will say —

or —

or some in-between comment.

For inspiration, run that program when you get up in the morning. Then notice whether your day turns out the way the computer predicts!