?
Solved

Find out if coordinate has a text character there>>100 points

Posted on 1998-06-08
7
Medium Priority
?
196 Views
Last Modified: 2010-04-16
I'm having some trouble with a small program i'm writing for fun.  You see, i have this little ascii character that moves around.  What i would like is that i can load a text file, which is displayed onscreen, and if a text character is there, it acts as a wall.  Basically i need some sort of boolean thing that just tells me if a character is writtne there.  THANKS
0
Comment
Question by:hansell
7 Comments
 
LVL 2

Accepted Solution

by:
kellyjj earned 300 total points
ID: 1217098
YOu can do it like this

if mem[b800:0000]='C' then dothis;

the offset inside the mem[] is the memory location for video.  You can read it just like that. However, and I don't remember off the top of my head which is,  even addresses are for attributes, odd for the char. (Could be the other way).
0
 
LVL 1

Expert Comment

by:shivers
ID: 1217099
he's right about the B800 address, but to access it use this formula:

offset := ((y * 80) + x) * 2

where x and y are the coordinates on the screen (zero based - ie 0-79, 0-24 not 1-80,1-25).  The reason for the *2 is that there is one byte for the attribute of the character (ie colour, flashing, etc) and the other is the ASCII code.

I can't quite remember which way round the bytes are though - if that doesnt work just add 1 to the offset.

then use this:

ch := mem[B800:offset];

or to make it faster, embed the equation in the mem[] call.

This is the best way to do this - can be up to 100 times faster than going through the BIOS - let alone a Pascal call.
0
 

Author Comment

by:hansell
ID: 1217100
Thanks for your help, I'll try to work with that...

But if you have any small snippets of code where this is done, that would be much appreciated, considering I don't quite understand all of what you have explained  ):


0
Take Control of Web Hosting For Your Clients

As a web developer or IT admin, successfully managing multiple client accounts can be challenging. In this webinar we will look at the tools provided by Media Temple and Plesk to make managing your clients’ hosting easier.

 

Author Comment

by:hansell
ID: 1217101
Well, i think i'm doing everything as I was told...but I get an 'unknown identifyer' for 'b800' and i'm not sure what to make it? Here is my snippet of code I was using...

program chartest;

uses crt;

var
offset:integer; {I assume offset would be an integer}

begin
gotoxy(1,1);
writeln('c');
offset:=((1*80)+1)*2; {the "1"'s are the coordinates}

if mem[b800:offset] then  {the b800 is an "unknown identifyer"}
begin
writeln('A character is there!');
end;
end.

NOTE:  I just want the simplest way of doing this, no speed efficiency is required.
0
 

Author Comment

by:hansell
ID: 1217102
Wait!!  I think i know SOMETHING i did wrong...i need to use $b800, so that's one thing solved...but i have another problem then..look at the comments...

Part of above code:
-----------------------------------------------------------------
     if mem[b800:offset] then {I get boolean expression expected?}
     begin
     writeln('A character is there!');
     end;
     end.
-----------------------------------------------------------------

HELP ME PLEASE!!!!!!  I'M DROWNING

0
 

Expert Comment

by:Mukke
ID: 1217103
You need to tell the program what it is looking for:
you either of these as I don't recall of what type mem is.
In the first I use typecasting (turning a variable into another, char)

if char(mem[b800:offset]) = " " then ......
if mem[b800:offset] = " " then ......
if mem[b800:offset] = 32 then ......

I think 1 and 3 results in the same, however I'm not sure.

Mukke

0
 

Expert Comment

by:Mukke
ID: 1217104
Sorry..... the above will trigger if there is NOT a character there. Simply add a NOT after IF or change = to <>

Mukke
0

Featured Post

Get expert help—faster!

Need expert help—fast? Use the Help Bell for personalized assistance getting answers to your important questions.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Virtualization software lets you run different versions of Windows, Ubuntu Linux and other versions of Linux all at the same time, rather than running each one directly from your computer's hard drive.
Washington based MSP turned to OnPage to solve their needs for after-hours alerting when customers’ technologies failed. In this post  see how DNS benefited from rolling out OnPage as a solution: -Preserve their SLAs -Improve response time by…
How to fix display issue, screen flickering issue when I plug in power cord to the machine. Before I start explaining the solution lets check out once the issue how it looks like after I connect the power cord. most of you also have faced this…
In this video I will demonstrate how to set up Nine, which I now consider the best alternative email app to Touchdown.
Suggested Courses
Course of the Month6 days, 12 hours left to enroll

593 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question