8086 program to Subtract two 8 bit numbers

13:07


ØØ       Explanation :
·            Consider that a byte of data is present in the AL register and second byte of data is present in the BL register.
·            We have to subtract the byte in BL from the byte in AL. Using sub instruction subtract the contents of two registers. Result will be stored in the AL register.


·            Display the result using display routine.
For example :
AL = 0A H

0A H
(10)10

BL = 04 H
–
04 H
(4)10



06H

ØØ       Algorithm :
Step 1      :    Initialise the data segment.
Step 2      :    Get the first number in AL register.
Step 3      :    Get the second number in BL register.
Step 4      :    Subtract the two numbers.                                                          Corel – 2               
Step 5      :    Display the result.    
Step 6      :    Stop
ØØ       Flowchart : Refer flowchart 9.

ØØ       Program :
.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
ØØ       Result :
C:\>tasm 8bit-sub.asm
Turbo Assembler  Version 3.0  Copyright (c) 1988, 1991 Borland International
Assembling file:   8bit-sub.asm
Error messages:    None
Warning messages:  None
Passes:            1
Remaining memory:  438k
C:\>tlink 8bit-sub.obj
Turbo Link  Version 3.0 Copyright (c) 1987, 1990 Borland International
Warning: No stack
C:\>8bit-sub
06
C:\>