Write a Program to Subtract Two 8 Bit Numbers in Assembly Language. Program will load two numbers in two registers and then subtract those numbers from one another . It should then display final result as the output of the program .

 

 

Program to Subtract Two 8 Bit Numbers

.model small  
 .data  
 a db 0AH                                                              
 b db 04H  
 .code  
      mov      ax, @data      ; Initialize data section  
      mov      ds, ax  
      mov      al, a          ; Load number1 in al  
      mov      bl, b          ; Load number2 in bl  
      sub      al, bl         ; subtract numbers and result in al  
      mov      ch, 02h        ; Count of digits to be displayed  
      mov      cl, 04h        ; Count to roll by 4 bits  
      mov      bh, al         ; Result in reg bh  
 l2:     rol      bh, cl      ; roll bl so that msb comes to lsb   
      mov      dl, bh         ; load dl with data to be displayed  
      and      dl, 0fH        ; get only lsb  
      cmp     dl, 09          ; check if digit is 0-9 or letter A-F  
      jbe      l4  
      add      dl, 07         ; if letter add 37H else only add 30H  
 l4:     add      dl, 30H  
      mov      ah, 02         ; Function 2 under INT 21H (Display character)  
      int      21H  
      dec      ch             ; Decrement Count  
      jnz      l2  
      mov      ah, 4cH        ; Terminate Program  
      int      21H  
      end