Assembly Language Programming 3

Output

Output to screen.

To output a single character to the screen, you need to do three things...

Example

This program would output the character 'A' to the screen.

MOV AH,2
MOV DL,65
INT 21H

Special characters may be used..

ASCII code Character
7 Beep
8 Backspace
9 Tab
10 Line Feed
13 Carriage Return

Example program

This program outputs the character whose ASCII code is stored in store location 'FirstLetter'.

program OutLetter;    
var FirstLetter : byte; {1 byte store location}
begin    
  FirstLetter := 65; {Give value to 'FirstLetter'}
  asm {start of Assembly program}
  mov dl,FirstLetter; {Transfer character code from 'FirstLetter' to DL}
  mov ah,2 { Initialise for output}
  int 21h; {Output character}
  end; {end of Assembly language}
end.    

Exercises

1. Write a program to output the word 'TEN' onto the screen, followed by a 'Beep'.
2. Write a program which outputs the word

T
E
N

vertically on the screen.

(You will by now be discovering that it takes a lot of instructions in Assembly language to do even the simplest of tasks!)

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