I wrote a program in assembler and compiled it. It is meant to print a blue smiley face and then wait for the user to press a key before it terminates. It does do that last bit but it doesn't print the smiley face. Can someone explain what have I done wrong ?
CSEG segment
org 100h
Begin:
mov ax,0B800h
mov es,ax
mov di,0
mov ah,31
mov al,1
mov es:[di],ax
mov ah,10h
int 16h
int 20h
CSEG ends
end Begin
I compiled it with MASM with a 16 bit linker
It's been about a year or so since I worked with MASM and the only reference book I have at home is MIPS, so I'm admittedly a bit rusty, however print to screen requires a system interrupt (int 21h), yet the only system interrupt I'm seeing is the program termination call after the keyboard interrupt.
You can only poke the video buffer directly if you're in a text-only video mode. I'm guessing that you're using Windows of some kind and not actually booting DOS, so you probably are in a graphics mode.
What you may be able to do is open a console window and then AltEnter to go to a full-screen text mode. Try running your program there.