8086 Program to pack the two unpacked BCD numbers

11:34


ØØ       Explanation :
·            We have two digits available in the AL and BL registers in unpacked BCD form. The digit in BL is the LSB, whereas digit in AL is MSB. To pack the two numbers, means to combine the two numbers.
·            To make the digit in AL as MSB we rotate it 4 times to the left. i.e. if digit = 09 H, after rotating it by a 4 times it becomes 90 H. Now add the two numbers. Result will be packed BCD. Display the result.
                        eg. :                AL          = 09 N
                                                BL          = 02 H
                                                Result     = 92 H
ØØ       Algorithm :
Step I        :   Initialize the data memory.
Step II      :   Load the most significant BCD digit in AL.
Step III     :   Load the least significant BCD digit in BL.
Step IV     :   Rotate MSB 4 times to left.
Step V       :   Add least significant BCD digit into
                  ;   rotated number.
Step VI     :   Display the result.
Step VII   :   Stop.
ØØ       Flowchart : Refer flowchart 5.



ØØ       Program :
.model small                                                                                         
.data
a db 09H
b db 02H
.code
       mov     ax,@data       ; Initialize data section
       mov     ds,ax
       mov     al,a               ; Load number1 in al
       mov     bl,b              ; Load number2 in bl
       rcl       al,4              ; rotate first number 4 times to make it 90h
       add      al,bl              ; add 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:\programs>tasm packbcd.asm
Turbo Assembler  Version 3.0  Copyright (c) 1988, 1991 Borland International
Assembling file:   packbcd.asm
Error messages:    None
Warning messages:  None
Passes:            1
Remaining memory:  438k
C:\programs>tlink packbcd.obj
Turbo Link  Version 3.0 Copyright (c) 1987, 1990 Borland International
Warning: No stack
C:\programs>packbcd
92
C:\programs>