Task

Cause a line printer attached to the computer to print a line containing the message:    Hello World! 



Note

A line printer is not the same as standard output.

A   line printer   was an older-style printer which prints one line at a time to a continuous ream of paper.

With some systems, a line printer can be any device attached to an appropriate port (such as a parallel port).




;Assemble with: tasm, tlink /t
;assume direction bit is clear (so si increments)
        .model  tiny
        .code
        org     100h
start:  mov     si, offset msg  ;point to message
        jmp     pr20
 
pr10:   mov     ah, 0           ;write character to printer
        mov     dx, 0           ;LPT1
        int     17h
pr20:   lodsb                   ;al, ds:[si++]
        cmp     al, 0           ;terminator?
        jne     pr10            ;loop if not
        ret                     ;return to OS
 
msg     db      "Hello World!", 0ch, 0  ;0ch = form feed (for laser printer)
        end     start