Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!csun!Twg-S5!abcscnuk
From: abcscnuk@Twg-S5.uucp (Naoto Kimura (ACM))
Newsgroups: comp.lang.pascal
Subject: Re: address screen memory
Message-ID: <1990Oct15.110743.15901@csun.edu>
Date: 15 Oct 90 11:07:43 GMT
References: <4249@gara.une.oz.au>
Sender: news@csun.edu (News Administrator)
Organization: csun
Lines: 87

In article <4249@gara.une.oz.au> nveldhov@gara.une.oz.au (Kick_Butt alias of nICK ) writes:
]Hello
]
]I am only new at TURBO PASCAL, and just starting to write programs in this
]great language.
]
]Getting to the point, does somebody out there have any code that can read the
]character and color at any location on the screen.  I thought that this could
]be done by getting directly into the screen memory. I would appreciate any help
]    
]   THANK YOU.
]
](uses TURBO PASCAL version 5.5)

Get the book "Programmers Guide to PC/AT/PS2 Video Systems" by Richard
Wilton(?) printed by Microsoft Press.  It discusses techniques for
detecting, reading from, and writing to the video display.  I found it
to be a great source of information about the different video display
hardware systems that can be installed on the IBM-PC.

Here's a bits of code that you could probably use until you get the
book:

---- CUT HERE ----
    unit Screen;

    interface

    uses
	Dos;

    const
	MDA_seg	= $b000;
	CGA_seg	= $b800;

    type
	ScreenChar = record
	    Ch	: Char;
	    Attr	: Byte
	    end;

    const
	ScrnSeg	: Word = CGA_seg;

    var
	ScreenRows	: Word;
	ScreenColumns	: Word absolute $40:$4A;

    procedure ScreenPeek( x,y : Integer;  var S : ScreenChar );
    procedure ScreenPoke( x,y : Integer;  S : ScreenChar );

    implementation

    procedure ScreenPeek( x,y : Integer;  var S : ScreenChar );
	begin
	    if (x>0) and (x<=ScreenColumns)
	     and (y>0) and (y<=ScreenRows) then
		S := ScreenChar(memw[ScrnSeg:
				    (y-1)*ScreenColumns + (x-1)])
	end;

    procedure ScreenPoke( x,y : Integer;  S : ScreenChar );
	begin
	    if (x>0) and (x<=ScreenColumns)
	     and (y>0) and (y<=ScreenRows) then
		memw[ScrnSeg:(y-1)*ScreenColumns + (x-1)] := Word(S)
	end;

    var
	regs:Registers;
    begin
	ScreenRows := 25;
	intr($11,regs);
	if (regs.ax and $30) = $30 then begin
	    ScrnSeg := MDA_seg
	  end
	else begin
	    ScrnSeg := CGA_seg
	  end
    end.
---- CUT HERE ----

                //-n-\\			 Naoto Kimura
        _____---=======---_____		 (abcscnuk@csuna.csun.edu)
    ====____\   /.. ..\   /____====
  //         ---\__O__/---         \\	Enterprise... Surrender or we'll
  \_\                             /_/	send back your *&^$% tribbles !!