function GetParamStr(P: PChar; var Param: string): PChar;
var
  Len: Integer;
  Buffer: array[0..4095] of Char;
begin
  while True do
  begin
  while (P[0] <> #0) and (P[0] <= ' ') do Inc(P);
  if (P[0] = '"') and (P[1] = '"') then Inc(P, 2) else Break;
  end;
  Len := 0;
  while (P[0] > ' ') and (Len < SizeOf(Buffer)) do
    if P[0] = '"' then
    begin
      Inc(P);
      while (P[0] <> #0) and (P[0] <> '"') do
      begin
        Buffer[Len] := P[0];
        Inc(Len);
        Inc(P);
      end;
      if P[0] <> #0 then Inc(P);
    end else
    begin
      Buffer[Len] := P[0];
      Inc(Len);
      Inc(P);
    end;
  SetString(Param, Buffer, Len);
  Result := P;
end;


function ParamCount: Integer;
var
  P: PChar;
  S: string;
begin
  P := GetParamStr(GetCommandLine, S);
  Result := 0;
  while True do
  begin
    P := GetParamStr(P, S);
    if S = '' then Break;
    Inc(Result);
  end;
end;

Technical Note - You may not know it, but Delphi creates and starts it's own "Memory Manager" in the System.pas . The System.pas Unit will always start up a Memory Manager for your Delphi program (or library) when your program initilizes, (starts execution). This Memory Manager sets up it's own Heap memory block to assign and allocate, this Memory Manager handles the memory use for non-fixed size variables, which include variables like type "String", "PChar" and Dynamic Arrays. Also Calls to GetMem( ) and FreeMem( ) will use the memory Manager. This is one of the reasons that the Delphi program file size starts out at 16 Kbs. Without this Memory Manager, Delphi would not have the Long String methods that are so convient and easy

Program file .DPR coding is diferent than Unit coding

If you are used to coding in the Delphi Form Unit, you will notice that the Program .DPR file does NOT have a interface section or a implementation section like the Unit has. Also in the Unit .PAS file, there is NO   begin  and   end.  code block.

type
  TForm1 = class(TForm)
    Button1: TButton;
  private
    { Private declarations }
  public
    { Public declarations }
  end;

When you did coding in a Form Unit's Implementation section, you did Not need to be aware of the order of your procedure and function definitions. When working above the main begin line in a .dpr file, you will need to place any procedure you call from another procedure ABOVE that procedure that calls it. The compilier will read your code from Top to Bottom when it assembles your program. So it does Not know about any code below the line of code it is currently reading and any procedures that are called on that line, will have to be defined Above that line. If you find that you need to call a procedure and can Not move it above the line that calls it, you can use the   forward   compilier directive. The purpose of a forward declaration is to extend the reading of a procedure or function definition to an earlier point in your code. This allows other procedures and functions in the .dpr file to call the forward-declared routine before it is actually defined.

Message Boxes
In the next program I will use the standard Windows System "Message Box" to get some user input. If you look at the Win32 API Help in it's index for "Message Boxes", or go to the MSDN web site page for MSDN-MessageBox you will find some information about Message Boxes. Now Look in the API Help for "MessageBox" and there is the function definition for MessageBox( ) and the parameter options and use. The MessageBox function is defined in the API Help "C" as - -

int MessageBox(
    HWND hWnd,	// handle of owner window
    LPCTSTR lpText,	// address of text in message box
    LPCTSTR lpCaption,	// address of title of message box  
    UINT uType 	// style of message box
   );

function MessageBox(hWnd: Cardinal; lpText, lpCaption: PChar; 
                     uType: Cardinal): Integer;

MessageBox(hMainWindow,'There was an Error somewhere',
    ' ERROR, you got an Error', MB_OK or MB_ICONERROR);

Using API Function Flags
In most API functions there will be ways to change what the function does and other options for that function. A very common way is to use numereic Flags in a parameter like in the fourth parameter of the MessageBox( ) function above. Since this method is used so much, some explanation may help you understand it. You may be used to the Object Oriented Pascal methods of Option selection, API (other than COM) isn't Object Oriented, so API fuctions are used to create and change things. One method for setting options in a function is with Numeric Constants like MB_ICONERROR. In windows.pas some of the message box Flags are definded as - -

const
  MB_OK = $00000000;
  MB_OKCANCEL = $00000001;
  MB_ABORTRETRYIGNORE = $00000002;
  MB_YESNOCANCEL = $00000003;
  MB_YESNO = $00000004;
  MB_RETRYCANCEL = $00000005;

  MB_ICONERROR = $00000010;
  MB_ICONQUESTION = $00000020;
  MB_ICONWARNING = $00000030;
  MB_ICONASTERISK = $00000040;

  MB_DEFBUTTON1 = $00000000;
  MB_DEFBUTTON2 = $00000100;
  MB_DEFBUTTON3 = $00000200;

  MB_APPLMODAL = $00000000;
  MB_SYSTEMMODAL = $00001000;
  MB_TASKMODAL = $00002000;

Note - - PChar( ) typecast
I have seen an abundance of code presented for using API functions where a Charater Array (text with two ' ) in the parameters will be TypeCast as a PChar( ), , , , like this -

MessageBox(hMainWindow,PChar('There was an Error somewhere'),
    PChar(' ERROR, you got an Error'), MB_OK or MB_ICONERROR);

MessageBox(hMainWindow,'There was an Error somewhere',
    ' ERROR, you got an Error', MB_OK or MB_ICONERROR);

Getting info from the OS
This program will show several ways to get charater strings from Windows OS functions, see the GetWindowsDirectory( ), GetCurrentDirectory( ) and GetComputerName( ) functions in the code below. When geting a PChar from windows OS, you will have to deal with making sure your variables that recieve null-terminated strings have enough memory for this string. There is more infomation about the PChar Variable type and API pointers, in the Lesson 4 web page, Using PChar in API functions, and Pointers.

1. procedure GetLocalTime(var lpSystemTime: TSystemTime);
       MSDN-GetLocalTime
2. function GetWindowsDirectory(lpBuffer: PAChar; uSize: Cardinal): Cardinal;
       MSDN-GetWindowsDirectory
3. function GetSystemDirectory(lpBuffer: PChar; uSize: Cadinal): Cardinal;
       MSDN-GetSystemDirectory
4. function GetComputerName(lpBuffer: PChar; var nSize: Cardinal): Boolean;
       MSDN-GetComputerName
5. function GetUserName(lpBuffer: PChar; var nSize: Cardinal): Boolean;
       MSDN-GetUserName
6. function GetSystemMetrics(nIndex: Integer): Integer;
       MSDN-GetSystemMetrics
7. function SystemParametersInfo(uiAction, uiParam: Cardinal; pvParam: Pointer; fWinIni: Cardinal): Boolean;
       MSDN-SystemParametersInfo
8. function GetVersionEx(var lpVersionInformation: TOSVersionInfo): Boolean;
       MSDN-GetVersionEx
9. function ExpandEnvironmentStrings(lpSrc: PChar; lpDst: PChar; nSize: Cardinal): Cardinal;
      MSDN-ExpandEnvironmentStrings
10. procedure GlobalMemoryStatus(var lpBuffer: TMemoryStatus);
        MSDN-GlobalMemoryStatus
11. function ShellExecute(hWnd: HWND; Operation, FileName, Parameters, Directory: PChar; ShowCmd: Integer): HINST;
        MSDN-ShellExecute

 
program Project1;
{This Program gets System Info to a text file and opens that
file in the default Text edit program. There is no GUI created
and No message loop is used. User interaction is done with
2 Message Boxes}

uses
  Windows, ShellApi;
  {ShellApi is added to use ShellExecute( )}

{$R *.RES}

var
WinDir: Array[0..4095] of Char;
{WinDir: Array[0..65535] of Char;}
{Getting PChar strings from the Windows OS requires
the recieving var to have memory for that string.
An array of Char does not change it's memory use like
a PChar or String var. Using a Larger array of Char
will make sure you have enough space for the string.
I use Array[0..4095] alot, 4 Kb will be more than
is needed most of the time, If you need it for a
Multiline Edit then Array[0..65535] will cover the
max size of it's text buffer}

WindowsDir, SystemDir, CurrentDir, ComName, UserName: String;
Transfer: PChar;
SystemTime1: TSystemTime;
ScreenWidth, ScreenHeight, WinBorder: Integer;
CharSize: Cardinal;
GotMouse, ShowSound: Boolean;
GotVersion: Boolean = False;
WorkRect: TRect;
OSVersionInfo1: TOSVersionInfo;

const
TxtFile = 'C:\Info Folder\System Info.txt';

function Int2Str(Number : Int64) : String;
var Minus : Boolean;
begin
{SysUtils is not in the Uses Clause so I can not use IntToStr( )
and have to define an Int2Str( ) function here}
   Result := '';
   if Number = 0 then
      Result := '0';
   Minus := Number < 0;
   if Minus then
      Number := -Number;
   while Number > 0 do
   begin
      Result := Char((Number mod 10) + Integer('0')) + Result;
      Number := Number div 10;
   end;
   if Minus then
      Result := '-' + Result;
end;


procedure MakeTextFile;
  var
  File1: TextFile;
  MemStatus: TMemoryStatus;
begin
AssignFile(File1, TxtFile);
{$I-}
Rewrite(File1);
{$I+}
if IOResult = 0 then
  begin
  WriteLn(File1,'           the Time is '+Int2Str(SystemTime1.wHour)+':'
    +Int2Str(SystemTime1.wMinute));
  WriteLn(File1,'           This File is '+TxtFile);
  WriteLn(File1,'This Program is '+ParamStr(0));
  WriteLn(File1,'Windows Folder is '+WindowsDir);
  WriteLn(File1,'Windows System Folder is '+WinDir {SystemDir});
  {WinDir, Array of Char can be used as a String}
  WriteLn(File1,'Current Folder is '+CurrentDir);
  WriteLn(File1,'Computer Name is '+ComName);
  WriteLn(File1,'User Name is '+UserName);

{ExpandEnvironmentStrings is used to get DOS environment info}
  if ExpandEnvironmentStrings('%PATH%',WinDir,512) <> 0 then
    WriteLn(File1,'Path is - '+WinDir);
  if ExpandEnvironmentStrings('%TMP%',WinDir,MAX_PATH) <> 0 then
    WriteLn(File1,'TMP is - '+WinDir);

  if GotMouse then
    WriteLn(File1,'Mouse is Present')
    else WriteLn(File1,'No Mouse is Present');
  if ShowSound then
    WriteLn(File1,'Sounds are made Visible')
    else WriteLn(File1,'Sounds are Not made visible');
  WriteLn(File1,'Screen Work Area Rectangle Top is '+Int2Str(WorkRect.Top)+
    ' Left is '+Int2Str(WorkRect.Left)+' Bottom is '+Int2Str(WorkRect.Bottom)
    +' Right is '+Int2Str(WorkRect.Right));
  WriteLn(File1,'Windows Sizing Border multiplier is  '+Int2Str(WinBorder));
  WriteLn(File1,'Screen Width is '+Int2Str(ScreenWidth)+' Screen Height is '
    +Int2Str(ScreenHeight));

  MemStatus.dwLength := SizeOf(MemStatus);
  {TMemoryStatus has a Size variable so you have to intialize it}
  GlobalMemoryStatus(MemStatus);
  {GlobalMemoryStatus gets memory and page file info}
  WriteLn(File1,'Tolal System Memory is '+Int2Str(MemStatus.dwTotalPhys)
    +' bytes -  Total Page File is '+Int2Str(MemStatus.dwTotalPageFile)
    +' Memory Load is '+Int2Str(MemStatus.dwMemoryLoad)+'%');

  if GotVersion then
    begin
    WriteLn(File1,'Windows Major Version is '
    +Int2Str(OSVersionInfo1.dwMajorVersion)
    +' Minor Version is '+Int2Str(OSVersionInfo1.dwMinorVersion)
    +' CSDversion is'+OSVersionInfo1.szCSDVersion);
    if OSVersionInfo1.dwPlatformId = VER_PLATFORM_WIN32_NT then
    WriteLn(File1,'This is a windows NT system');
    end;
  end;
{$I-}
CloseFile(File1);
{$I+}
if IOResult = 0 then
ShellExecute(0, 'open', TxtFile, nil, nil, SW_SHOWNORMAL);
{ShellExecute( ) is included here because it is a very useful function.
Here it displays the "System Info.txt" so I do not have to make a GUI
with a Multiline Edit control to show it. It can also be set to do the same
with NotePad.exe instead of the default, like this
ShellExecute(0, 'open', 'Notepad.exe', TxtFile, nil, SW_SHOWNORMAL);}
end;


begin  // / / / / MAIN PROGRAM BEGIN / / / /
GetLocalTime(SystemTime1);
{GetLocalTime will find out the Date and Time}

{when geting a PChar from windows OS, you will have to deal
with getting and setting the amount of memory needed
for the PChar, Array of Char, or String. The following
examples will show different methods of getting strings}

GetWindowsDirectory(WinDir, MAX_PATH);
{WinDir is a Fixed length array of Char, the array can be
larger than the amount of charaters needed, but not smaller.
See the various array lengths in the var clause above.
MAX_PATH is a const used for the Maximum number of charaters
allowed in a path string}

WindowsDir := String(WinDir);

GetSystemDirectory(WinDir,GetSystemDirectory(WinDir,1)+1);
{the result of GetSystemDirectory(WinDir,1) is the length of
the PChar string for the System Directory, add 1 for the
null charater at the end of a PChar string}
SystemDir := String(WinDir);

SetLength(CurrentDir,GetCurrentDirectory(1,nil));
{You can use a pascal String to get the PChar string if you
SeLength( ) to the amount of characters needed and then
typecast the String to PChar}
GetCurrentDirectory(Length(CurrentDir)+1,PChar(CurrentDir));

CharSize := MAX_COMPUTERNAME_LENGTH + 1;
{the computerName has a max length, given in
MAX_COMPUTERNAME_LENGTH, so you can use this to set the memory
needed for the PChar string, it's OK if it's more than is needed}
GetMem(Transfer, CharSize);
{allocate memory to the Transfer variable
Always use FreeMem( ) after a GetMem}
GetComputerName(Transfer, CharSize);
ComName := String(Transfer);
FreeMem(Transfer);

GetUserName(nil,CharSize);
{GetUserName(nil,CharSize) gets the length of the
UserName string into the CharSize var}
SetLength(UserName,CharSize);
GetUserName(@UserName[1],CharSize);
{the address of the first Charater of the String
@UserName[1] is used instead of a PChar typecast}


ScreenWidth := GetSystemMetrics(SM_CXSCREEN);
{GetSystemMetrics( ) can get you alot of useful info
see API help for the List of parameters}
ScreenHeight := GetSystemMetrics(SM_CYSCREEN);
GotMouse := Boolean(GetSystemMetrics(SM_MOUSEPRESENT));

SystemParametersInfo(SPI_GETSHOWSOUNDS,0,@ShowSound,0);
{SystemParametersInfo( ) can get and set some System settings}
SystemParametersInfo(SPI_GETWORKAREA,0,@WorkRect,0);
SystemParametersInfo(SPI_GETBORDER,0,@WinBorder,0);

OSVersionInfo1.dwOSVersionInfoSize := SizeOf(OSVersionInfo1);
{many Windows Record structures have a Size variable which
must be filled BEFORE the address of the Record is passed
to Windows}
if GetVersionEx(OSVersionInfo1) then
GotVersion := True;
{GetVersionEx will provide you with Windows version info
for the computer that is running this program
Notice that the variable OSVersionInfo1 does not need a @, like
the @WorkRect and @WinBorder used in the SystemParametersInfo,
there is only one Type of variable allowed in GetVersionEx,
but in SystemParametersInfo the variable can be a TRect, a Boolean
an Integer or other Type so a Pointer Type is used}


{All user input is from Message Boxs, and the Result (ID_YES) will
determine what is done
look in the API help for more MessageBox button and icon options}
if MessageBox(0,PChar('Today is '+Int2Str(SystemTime1.wMonth)+'/'
     +Int2Str(SystemTime1.wDay)+'/'
     +Int2Str(SystemTime1.wYear)+#10
     +'Do you want to create the Folder "Info Folder" ? ?'
     +#10+'To place a System Info.txt file with System Information'),
     'Make Folder ?',  MB_YESNO or MB_ICONQUESTION or MB_DEFBUTTON2 
     or MB_SETFOREGROUND) = ID_YES then
  begin
  if  CreateDirectory('C:\Info Folder',nil) then
    begin
    {in the MessageBox function there is the hWnd, handle of owner window,
     which is the window handle to return focus to, after the message box.
     You would set your Main Window handle here, but there is no Main
     Window in this App so I set it to 0 instead.}

  if MessageBox(0,'Do you want to create the File "System Info.txt" ? ?',
    'Make File ?', MB_OKCANCEL or MB_ICONQUESTION) = ID_OK then
    MakeTextFile;
    end else
    MessageBox(0,'Could not create a Folder',
    ' ERROR, folder was not created', MB_OK or MB_ICONERROR)
  end;

end.

I will code in the .DPR program file in these first lessons, but using Units with your API programming is a good idea to help you with code organization. I will show some code in units in Lesson eleven.