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Comment by mrfinn | Hacker News Reader

These challenges are funny - they remind me of the old days. Back in the DOS/Windows days, we used to have the .com format, which was perfect for tiny programs. One could even write a program of less than 10 bytes that could actually do something!

We've come a long way since then, and is like, at some point, nobody cared about optimizing executable size anymore

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People in the embedded space care. Symbian OS was compiled for small size, only certain parts were allowed use O3, such as the jpeg decoder.

Some people care about executable size, (mostly) everyone else ships Electron apps.

Tell it to my boss, he wants his app last week.

I learned to write COM programs at some point but quickly unlearned it. There were some spots where you can use them and not .bat files, but outside of that it’s a lot.

  debug
  -a 100
  178A:0100 int 19
  178A:0102
  -r cx
  CX 0000
  :2
  -n reboot.com
  -w
  Writing 00002 bytes
  -q

Some more:

Quick'n'dirty:

    .model small
    .code
     org 100h
    start:
     int 19h                 ; Bootstrap loader
    end start

More "correct":

    .model small
    .code
     org 100h
    start:
     db 0EAh                 ; Jump to Power On Self Test - Cold Boot
     dw 0,0FFFFh
    end start

Even more "correct":

    .model small
    .code
     org 100h
    start:
     mov ah,0Dh
     int 21h                 ; DOS Services  ah=function 0Dh
                             ;  flush disk buffers to disk
     sti                     ; Enable interrupts
     hlt                     ; Halt processor
     mov al,0FEh
     out 64h,al              ; port 64h, kybd cntrlr functn
                             ;  al = 0FEh, pulse CPU reset
    end start

Great example, a two bytes reboot utility. From the times when we could turn off the computer with a push of a button without fearing a global catastrophe...

JMP FFFF:0000

INT 13h... uff chills

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