;www.hpkclasses.ir
;Assembly sample program
;January 01, 2008

    .MODEL small 
    .STACK 256 
    .DATA 
MSG1     DB 'Enter a lower case letter: $' 
MSG2     DB 0Dh,0Ah,'In upper case it is: ' 
CHAR     DB ?,'$' 
exCode   DB 0 
    .CODE 
MAIN: 
;initialize ds 
    mov     ax,@data     ; Initialize DS to address 
    mov     ds,ax        ; of data segment 
;print user prompt 
    mov     ah,9         ; display string fcn 
    lea     dx,MSG1      ; get first message 
    int     21h          ; display it 
;input a character and convert to upper case 
    mov     ah,1         ; read char fcn 
    int     21h          ; input char into AL 
    sub     al,20h       ; convert to upper case 
    mov     CHAR,al      ; and store it 
;display on the next line 
    mov     dx,offset MSG2 ; get second message 
    mov     ah,9         ; display string function 
    int     21h          ; display message and upper case 
;return to DOS 
Exit: 
    mov     ah,4Ch       ; DOS function: Exit program 
    mov     al,exCode    ; Return exit code value 
    int     21h          ; Call DOS. Terminate program 
    END     MAIN        ; End of program / entry point