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Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
The 21 you changed is not part of my program but code the assembler put in to terminate the program. I don't think 32 is defined as a standard DOS call so I have no idea what happens.
On the commandline type debug pattern3.com and use the u command several times to see the assembly code and you will see INT 21 at the end.
I learned this ages ago before internet and search engines by randomly typing in things to see what happened and gradually figuring out how it worked.
Registered Member #108
Joined: Thu Feb 09 2006, 11:44PM
Location: Billings, MT
Posts: 61
Cool. I've never used the command-line debug program before.
I also noticed that you can change the colors by messing with the line 'FEC375F6'. For instance, try 'FEC275F6'. For some reason, this makes the program use 256-bit colors it looks like.
Does each hex pair correspond to one assembly instruction? I've never really understood how it works after you compile...
Registered Member #32
Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549
Ken Aycock wrote ...
Does each hex pair correspond to one assembly instruction? I've never really understood how it works after you compile...
Unfortunately it's more complicated than that. Each two digit hex number is a byte. Some commands are single byte, some are two, some are three and so on.
Give me a little time and I'll come up with my own response.
If you want to learn assembler, this is a good tute. Years back I learnt asm from that. Wow, that feels like a long time ago...
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
One interisting thing to note is that if you run this under winxp it takes 740k or ram
I was somwhat suprised at how good it looked considering that it was being upscaled to 1400x1050, just the strait command prompt looks like crap
Now if I only had something arround that this would be usefull on... Not old enough ;)
I wonder how long it will be before we are writing code in C bragging about how you can run it on a 1ghz p4 with 256mb of ram 100mb of disk space, and a video card with 128mb of....
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
I also noticed that you can change the colors by messing with the line 'FEC375F6'. For instance, try 'FEC275F6'. For some reason, this makes the program use 256-bit colors it looks like.
That change breaks the loop that generates the blue palette so the program runs with the standard DOS palette.
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
Nice Bjorn, NT emulated dos will not show frame buffer blinking flags. However, if you run it full screen with this it will work. rem Try this in a batch file: %windir%\System32\CMD.EXE /C someapp
The classic prime number checker is a good exercise in ASM. You may find inline assembly inside C is often faster than linked ASM objects with the identical code or optimized C. A rather bizarre phenomena caused by virus scanners and Microsoft’s linker.
Here is a very old 5KB piano demonstrating IRQ chaining in the XP Virtual DOS window (file parser increases the size, no error handling, and not optimized.)
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Graphics demo to show off your old PC
I'm jealous
