KeyJ's DOS Weave Pattern

Author:          KeyJ / TRBL
Category:        Christmas Challenge 2023
System:          IBM PC or compatible
Language:        Assembly
Len source code: 266 bytes (minified assembly source)
Len exe file:    58 bytes (DOS .COM file)
Len code only:   58 bytes (DOS .COM files are code-only)

Instructions:
- assemble with yasm:
  $ yasm -f bin -o vc3kjdos.com vc3kjmin.asm
  - other assemblers should work too, but haven't been tested
- run in a DOS emulator like DOSBox:
  $ dosox vc3kjdos.com

Description:
Uses a simple parametric formula: X and Y in, character out.

Comments:
Same approach as with my Python implementation, except it uses a different
range for x so the results never become negative.

Note that the screenshots have been generated with different screen modes
to look nicer: vc3kjdos_result.png is "dosbox -machine cga" with 40-column
mode ("mode 40"); vc3kjdos_source.png is "dosbox -machine ega" in 43-line mode
(the source code is 32 lines long, so it couldn't fit onto one screen
otherwise).