Throughout human history, people try to make the biggest, the fastest, and — sometimes — the smallest. [Hellmood] falls into the latter category and proves it with a 64 byte interactive 3D raycasting application for MSDOS.
Why MSDOS? We suppose why not? The .COM file format is lean, and you can take over everything without a lot of work. If the program were huge, it wouldn’t be very impressive. There are 64 shades of gray which is odd looking these days, however there are versions that use various color palettes and each one fits in 64 bytes or less. There’s even mouse control and you can see the results in the video below.
There were even some versions that didn’t do 3D and ray tracing that fit in 43 bytes, but that’s not as impressive visually. As you might expect, the code is written in assembly:
We looked at the code and recognized a BIOS call to set the video mode to 13 hex and some direct port output to the VGA video DAC at 0x3C9. We got lost after that, but it is certainly an economical program even if we can’t see how it is reading the mouse.
If you get the urge to do some MSDOS programming yourself, you can use gcc although you will almost surely get bigger executables. If you are just nostalgic for old games and software, you can run those in your browser.