Switching off computer

Here is some code posted by smiddy on the DexOS forum for that, it is coded to run in real mode, and does not use any DexOS functions so should work fine in dos.

Code:

   mov ax,5300h                     ; See if APM available   mov bx,0                         ; device = BIOS   int 15h   mov   dx,NoPowerManagment   jc .Error   cmp ax,101h                      ; See if version 1.1 or greater   mov dx,WrongVersion   jc .Error   mov [PowerManagmentVersion],ax   mov ax,5301h                     ; Do a real mode connection   mov bx,0                         ; device = BIOS   int 15h   jnc .NoConnectionError   cmp ah,2                         ; Pass if already connected   mov   dx,ErrorMessage              ; else error   jnz .Error.NoConnectionError:   mov ax,530eh                     ; Enable latest version of APM   mov bx,0                         ; device = BIOS   mov cx,[PowerManagmentVersion]   ; version   int 15h   mov   dx,ErrorMessage   jc .Error   mov ax,530dh                     ; Now engage and enable CPU management   mov bx,1                         ; device = all   mov cx,1                         ; enable   int 15h   mov   dx,ErrorMessage   jc .Error   mov ax,530fh   mov bx,1                         ; device = ALL   mov cx,1                         ; enable   int 15h   mov   dx,ErrorMessage   jc .Error   mov ax,5307h                     ; Do the power down   mov bx,1                         ; device = ALL   mov cx,3                         ; mode = OFF   int 15h                          ; shutdown CPU   mov   dx,ErrorMessage.Error:    mov   ah,9    int   21h   jmp  $             ; Error just loopPowerManagmentVersion dw 0NoPowerManagment      db 'No power management functionality',24hErrorMessage          db 'Power management error',24hWrongVersion          db 'Need APM version 1.1 or better',24h