Switch Case Implementation, Easiest Implementation, Choice Assembly Language, ASM, MASM, NASM Switch CASE

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;Programmed by SAQIB KHAN ;Purpose: Obtain Choice from user/Implement case ;Dated: 15th-MAY-2012 .model small .stack 100h .data num1 db 97 num2 db 2 msg_add db 10, "Press 0 for Addition $" msg_sub db 10, "Press 1 for Subtraction $" msg_adc db 10, "Press 2 to add with carry $" message db 10, "Enter your choice: $" msg_wrong db 10, "Please enter correct choice $" msg_verify db 10, "First operand sholud be greater than 2nd,Please change input values $" .code main: mov ax,@data mov ds,ax lea dx,msg_add ;Display add message mov ah,9h int 21h lea dx,msg_sub ;Display subtract message mov ah,9h int 21h lea dx,msg_adc ;Display add message mov ah,9h int 21h lea dx,message ;Display choice message mov ah,9h int 21h ;;;;;;;;;;;;;;;;;;;; mov ah,1 ;read key from user int 21h mov ah,0 ;empty the ah ,upper part of ax sub al,30h ; subtract 30h to get exact value from ascii shl al,1 ; multiply number by 2 to get to the case cmp al,4 ;compare for validity jg check ;jump if al,greater than 4 mov bx,ax ;mov value of ax to bx for offset jmp cs:jmptble [bx] ;jumptable jmptble dw case0,case1,case2 ;cases check: lea dx,msg_wrong ;Display wrong choice mov ah,9h int 21h mov dl,10 ;Move to new line mov ah,2h int 21h jmp main ;Loop again to get correct choice case0: ;Case0- Addition mov dl,10 ;move to new line mov ah,2h int 21h mov al,num1 ;copy num1 to al xor ah,ah ;empty ah to zero add al,num2 ; add num2 to al call display jmp endlabel ;jum to endlabel case1: ;Case1 for subtraction mov dl,10 ;;Move to new line mov ah,2h int 21h mov cl,num1 ;Copy number1 to cl cmp cl,num2 ;check if first numbr is smaller than second jl verify ;jump if num1 is less than num2 mov al,num1 ;copy num1 to al xor ah,ah ;empty the uper portion of ax sub al,num2 ;subtract two nmbers call display jmp endlabel case2: mov dl,10 mov ah,2h int 21h mov al,num1 xor ah,ah adc al,num2 ;adc add 1 value to the sum (if carry flag is 1) call display jmp endlabel verify: lea dx,msg_verify mov ah,9 int 21h display: mov dl,10 ;mov dl,10 to divide result in ax div dl ;Dvide ax by 10 mov dl,al ;copy quotient to dl mov bl,ah ;copy remainder to bl add dl,30h ;add 30h to get actual number mov ah,2h ;Service # to display character int 21h ;Call OS to do the job add bl,30h ;add 30h to remainder mov dl,bl ;move to dl to display mov ah,2h ;Service # to display character int 21h ;Call OS to do the job ret endlabel: mov ah,4ch int 21h end main

Simplest Implementaion of Switch Case in Assembly Language .asm file MASM file 32-bit/64bit

;Programmed by SAQIB KHAN
;Purpose: Obtain Choice from user/Implement case
;Dated: 15th-MAY-2012

.model small
.stack 100h
.data
        num1 db 97
        num2 db 2
    msg_add db 10,  "Press 0 for  Addition $"
        msg_sub db 10,  "Press 1 for  Subtraction $"
    msg_adc db 10,  "Press 2 to add with carry $"
    message db 10,  "Enter your choice: $"
msg_wrong db 10,  "Please enter correct choice $"
msg_verify db 10, "First operand sholud be greater than 2nd,Please change input values $"
.code
main: 
        mov ax,@data
        mov ds,ax
                       
    lea dx,msg_add    ;Display add message
    mov ah,9h
    int 21h
   
    lea dx,msg_sub    ;Display subtract message
    mov ah,9h
    int 21h

    lea dx,msg_adc    ;Display add message
    mov ah,9h
    int 21h
   
    lea dx,message  ;Display choice message
    mov ah,9h
    int 21h
;;;;;;;;;;;;;;;;;;;;   
   
    mov ah,1                 ;read key from user
    int 21h
    mov ah,0                 ;empty the ah ,upper part of ax
   
    sub al,30h              ; subtract 30h to get exact value from ascii
   
    shl al,1                ; multiply number by 2 to get to the case
    cmp al,4                ;compare for validity
    jg check                ;jump if al,greater than 4
    mov bx,ax               ;mov value of ax to bx for offset
    jmp cs:jmptble [bx]          ;jumptable

jmptble dw case0,case1,case2 ;cases   
   

check:
    lea dx,msg_wrong        ;Display wrong choice
    mov ah,9h           
    int 21h
    mov dl,10            ;Move to new line
    mov ah,2h
    int 21h
    jmp main            ;Loop again to get correct choice
case0:                    ;Case0- Addition
    mov dl,10            ;move to new line
    mov ah,2h
    int 21h
   
    mov al,num1            ;copy num1 to al
    xor ah,ah            ;empty ah to zero   
    add al,num2             ; add num2 to al
    call display   
    jmp endlabel            ;jum to endlabel
case1:                    ;Case1 for subtraction
    mov dl,10            ;;Move to new line
    mov ah,2h
    int 21h

    mov cl,num1            ;Copy number1 to cl
    cmp cl,num2            ;check if first numbr is smaller than second
    jl  verify            ;jump if num1 is less than num2
   
    mov al,num1            ;copy num1 to al
        xor ah,ah            ;empty the uper portion of ax
        sub al,num2             ;subtract two nmbers
   
    call display   
    jmp endlabel
case2:
    mov dl,10
    mov ah,2h
    int 21h
   
        mov al,num1
        xor ah,ah   
        adc al,num2     ;adc add 1 value to the sum (if carry flag is 1)
   
        call display
        jmp endlabel

verify:   
        lea dx,msg_verify
    mov ah,9
    int 21h
display:
mov dl,10            ;mov dl,10 to divide result in ax
        div dl                ;Dvide ax by 10
        mov dl,al            ;copy quotient to dl
        mov bl,ah            ;copy remainder to bl
        add dl,30h                ;add 30h to get actual number
        mov ah,2h            ;Service # to display character
    int 21h                ;Call OS to do the job
    add bl,30h            ;add 30h to remainder
    mov dl,bl            ;move to dl to display
        mov ah,2h            ;Service # to display character
        int 21h             ;Call OS to do the job
        ret
   

endlabel:
    mov ah,4ch
    int 21h

end main