286Present

Author:   pdw
Category: Christmas Challenge
System:   286 PC, MS-DOS
Language: Assembler
Len source code: 663
Len exe file:    45
Len code only:   45
Instructions:
  Assemble with nasm: nasm -o 286vc3.com 286vc3.asm

  Run on the DOS prompt. Clear the screen first.
Description:
  The image is drawn by poking to video memory, relying on the diagonal 
  symmetry of the image. Three loops are used. The outer two control row
  and column. The inner loop switches between horizontal and vertical.
  The corner spots are thus visited twice, this overwrite is detected
  using the parity flag and the character is modified into a '+'.
  
  The first few opcodes might look weird: they're also used as data.