Your program is supposed to create a full red screen in MSDOS. The source of the binary (.com file) must be 5 bytes or less. No wild assumptions, the binary must work in MsDos, DosBox, and FreeDos alike. For winning, you have to post x86 assembler code which can be assembled with NASM (FASM) or directly the hex code of the binary. You can test you assembler code in an Online Dosbox.

Code Example (six bytes):

X les cx,[si]
inc sp
jmp short X+1

Try x86 asm code in an Online DosBox

Information on sizecoding for Msdos

"M8trix" might be helpful

Background information/ six bytes version

  • 1
    \$\begingroup\$ You've created redundant tags (tiny & sizecoding) we have code-golf which is for minimal byte count. \$\endgroup\$ Commented Sep 14, 2020 at 11:36
  • 10
    \$\begingroup\$ Why not open this to other languages? (or even requre a red graphical window rather than full screen). Restricting to x86 assembler on MSDOS makes the challenge too restrictive, perhaps unnecessarily so. Competition is mainly within each language anyway \$\endgroup\$
    – Luis Mendo
    Commented Sep 14, 2020 at 12:05
  • 12
    \$\begingroup\$ Also, don't require a mininum score (maximum byte count) \$\endgroup\$
    – Luis Mendo
    Commented Sep 14, 2020 at 12:33
  • 3
    \$\begingroup\$ Do you actually know this is possible? \$\endgroup\$
    – Jo King
    Commented Sep 14, 2020 at 12:37
  • 3
    \$\begingroup\$ So... I didn't know twt86.co existed. This is game changer - can finally post working TIO links for x86 PC DOS! \$\endgroup\$
    – 640KB
    Commented Sep 25, 2020 at 14:17

1 Answer 1


5 bytes

Byte values

0x56 0xC4 0x04 0xAB 0xC3

ASM mnemonic


View inside a DOS debugger

View inside a DOS debugger

(edit:) To clarify, this is NOT MY solution. The challenge is mirrored from www.pouet.net, as linked in the question. There, somebody posted a valid solution which i pasted here. (edit2: added byte values and image)

  • \$\begingroup\$ That is not 5 bytes. 1 character takes up 1 byte. \$\endgroup\$
    – matt
    Commented Sep 24, 2020 at 16:12
  • \$\begingroup\$ @matt you're right, posting the ASM mnemonics might not be enough. I added the byte values and an image of an debugger view for clarification. \$\endgroup\$
    – HellMood
    Commented Sep 25, 2020 at 6:59
  • \$\begingroup\$ Posting an answer from an external source without improvement, even if credit the original author, is still most likely copyright violation, and either way it is explicitly disallowed. \$\endgroup\$ Commented Oct 24, 2020 at 16:07
  • \$\begingroup\$ @RedwolfPrograms i am genuinely curious how copyright works on 5 bytes of code, when i created almost the same solution BEFORE and published a strong salted hash with it as a proof. (Please see here: pouet.net/topic.php?which=11991&page=1) Other than that your comment left me with a big grin, thank you :D \$\endgroup\$
    – HellMood
    Commented Oct 26, 2020 at 10:37
  • \$\begingroup\$ @HellMood Not sure who created what, but according to your own answer: "this is NOT MY solution" \$\endgroup\$ Commented Oct 26, 2020 at 12:31

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