I came across something cool the other day that I thought I'd share: a 25-byte long integer sort routine (that is to say, the routine itself is only 25 bytes long).

Here it is:

;---------------------------------------------------------------
; Sorts an array of ints. C-callable (small model). 25 bytes.
; void sort (int n, int a[]);
;
; Courtesy of David Stafford.
;---------------------------------------------------------------
      .model small
      .code
        public _sort
top:    mov     dx,[bx]   ; swap two adjacent ints
        xchg    dx,[bx+2]
        xchg    dx,[bx]
        cmp     dx,[bx]   ; in the right order?
        jl      top       ; no, swap them back
        inc     bx        ; go to the next integer
        inc     bx
        loop    top
_sort:  pop     dx        ; get return address (entry point)
        pop     cx        ; get count
        pop     bx        ; get pointer
        push    bx        ; restore pointer
        dec     cx        ; decrement count
        push    cx        ; save count
        push    dx        ; save return address
        jg      top       ; if cx > 0
        ret
       end