;===========================================================================
;
;  * * * * * * * * * * * * * * * *
;  * TI-OS Plus! 1.2 Readme File *
;  * * * * * * * * * * * * * * * *
;
;    File dated 02/27/2001 (MM/DD/YYYY)
;         created by Tijl Coosemans (tijlc@mail.com)
;
;===========================================================================

;===========================================================================
; * What It Does *
;===========================================================================

  TI-OS Plus! is an interrupt program (a program that runs at the
  background), which runs external modules. So by simply installing a
  module you can add extra or other functions to your TI-83...

;===========================================================================
; * How To Use It *
;===========================================================================

  Send the group file tiosplus.83g to your calculator. This should install
  the following programs:
	TIPLUS : the executable
	ZTIPLS : the assembly code
  To enable TI-OS Plus! run the program named TIPLUS. It will show
  'enabled' and quit, so you can continue doing whatever you want. To
  disable the workings just run TIPLUS again. It is safe to run basic
  programs but I recommend you to disable TI-OS Plus! when you run assembly
  programs. It is also safe to turn off your calculator and the calc will
  APD after about 2 minutes of no activity. An extra feature is that you
  can turn off the calc by pressing [alpha]+[on]. When you then turn it
  back on, you get (just as with apd) back to the place you turned it off.

  You can also run TIPLUS with a value in 'ans' to force a specific action.
  The following shows all the commands.
	1 : disables TI-OS Plus!
	2 : enables TI-OS Plus!
  If 'ans' contains any other value than the ones listed above, the program
  will run as described before. ( Notice that 'ans' is 0 after running
  TIPLUS. )
  This feature might come handy in combination with Assembly Programs. By
  example, you can change prgmA of ION by:
	:1:prgmTIPLUS
	:send(9prgm0ION		// 0 is theta
	:ClrHome
	:prgmTIPLUS
  This program will disable TI-OS Plus! (even if it is already disabled)
  before running ION and reenable it afterwards.

  Installing Modules
  ------------------
    It's really simple to install a module. The only thing you have to do,
    is send it to your calculator. You don't even need to disable
    TI-OS Plus! nor you need to reenable it afterwards.

;===========================================================================
; * History *
;===========================================================================

<-> version 1.2 - 20010227 -- size: 581 bytes
	* fixed the bug that caused the calc to crash sometimes when a non
	  prog/list var was created
	* fixed the bug that caused the calc to crash sometimes when you
	  had a lot of user vars
	* [alpha]+[on] works better now
	* a module has to start with a $A7 now
<-> version 1.1 - 20010224 -- size: 575 bytes
	* added [alpha]+[on] feature
	* now runs modules even when there hasn't been a key press
	* fixed a lot of severe bugs, it's a lot more stable
<-> version 1.0 - 20010210 -- size: 535 bytes
	* first release

;===========================================================================
; * Developing Modules *
;===========================================================================

  - TI-OS Plus! calls every module one by one as it encounters them in the
    prog/list table before the TI-OS interprets a possible key press.
  - Modules are run directly from their location in memory: they are not
    reallocated. However, they can reallocate themselves when necessary,
    but do know that only bytes 8265h-8382h are save.
  - At module startup the key pressed has been saved in acc. The key values
    are the same as what _getk (4A18h) returns. (0 means no key)
  - To have your program be recognised as a module the first byte needs to
    be a '$A7' (simply add a 'and a' at the beginning).
  - Remember that since your program will be called from an interrupt, you
    cannot use any rom calls (unless you make your program rom specific).
    You also cannot use the 'ei' command, unless you really know what your
    are doing. 'ei' enables interrupts again, so it can mess up the current
    interrupt handle, with all kinds of consequences...

  All questions, tips, comments,... are welcome at tijlc@mail.com