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8086_Assembly_Solutions_Q1_Q9.txt
============================================================
Question 1: Add two single-digit numbers
============================================================
.model small
.stack 100h
.data

msg1 db "Enter first digit: $"
msg2 db "Enter second digit: $"
msg3 db "Sum = $"

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h

    ;input first digit
    mov ah,1h
    int 21h
    mov cl,al
    sub cl,48

    ;newline
    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h

    ;input second digit
    mov ah,1h
    int 21h
    mov bl,al
    sub bl,48

    ;newline
    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;add
    add cl,bl

    ;print msg3
    mov ah,9h
    lea dx,msg3
    int 21h

    ;print result
    mov ah,2h
    mov dl,cl
    add dl,48
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main


============================================================
Question 2: Subtract second digit from first digit
============================================================
.model small
.stack 100h
.data

msg1 db "Enter first digit: $"
msg2 db "Enter second digit: $"
msg3 db "Result = $"

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h

    ;input first digit
    mov ah,1h
    int 21h
    mov cl,al
    sub cl,48

    ;newline
    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h

    ;input second digit
    mov ah,1h
    int 21h
    mov bl,al
    sub bl,48

    ;newline
    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;subtract
    sub cl,bl

    ;print msg3
    mov ah,9h
    lea dx,msg3
    int 21h

    ;print result
    mov ah,2h
    mov dl,cl
    add dl,48
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main


============================================================
Question 3: Uppercase letter to lowercase
============================================================
.model small
.stack 100h
.data

msg1 db "Enter an uppercase letter: $"
msg2 db "Lowercase = $"

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h

    ;input letter
    mov ah,1h
    int 21h
    mov cl,al

    ;newline
    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;convert to lowercase
    add cl,32

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h

    ;print result
    mov ah,2h
    mov dl,cl
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main


============================================================
Question 4: Lowercase letter to uppercase
============================================================
.model small
.stack 100h
.data

msg1 db "Enter a lowercase letter: $"
msg2 db "Uppercase = $"

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h

    ;input letter
    mov ah,1h
    int 21h
    mov cl,al

    ;newline
    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;convert to uppercase
    sub cl,32

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h

    ;print result
    mov ah,2h
    mov dl,cl
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main


============================================================
Question 5: Three uppercase letters -> lowercase, printed in reverse order (each on new line)
============================================================
.model small
.stack 100h
.data

msg1 db "Enter first uppercase letter: $"
msg2 db "Enter second uppercase letter: $"
msg3 db "Enter third uppercase letter: $"
msg4 db "Result (reversed, lowercase): $"

c1 db ?
c2 db ?
c3 db ?

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h
    mov ah,1h
    int 21h
    mov c1,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h
    mov ah,1h
    int 21h
    mov c2,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg3
    mov ah,9h
    lea dx,msg3
    int 21h
    mov ah,1h
    int 21h
    mov c3,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;convert all three to lowercase
    mov al,c1
    add al,32
    mov c1,al

    mov al,c2
    add al,32
    mov c2,al

    mov al,c3
    add al,32
    mov c3,al

    ;print msg4
    mov ah,9h
    lea dx,msg4
    int 21h
    mov dl,10
    mov ah,2h
    int 21h
    mov dl,13
    int 21h

    ;print in reverse order: c3, c2, c1 (each on new line)
    mov ah,2h
    mov dl,c3
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    mov dl,c2
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    mov dl,c1
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main


============================================================
Question 6: Three lowercase letters -> uppercase, printed in reverse order (each on new line)
============================================================
.model small
.stack 100h
.data

msg1 db "Enter first lowercase letter: $"
msg2 db "Enter second lowercase letter: $"
msg3 db "Enter third lowercase letter: $"
msg4 db "Result (reversed, uppercase): $"

c1 db ?
c2 db ?
c3 db ?

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h
    mov ah,1h
    int 21h
    mov c1,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h
    mov ah,1h
    int 21h
    mov c2,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg3
    mov ah,9h
    lea dx,msg3
    int 21h
    mov ah,1h
    int 21h
    mov c3,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;convert all three to uppercase
    mov al,c1
    sub al,32
    mov c1,al

    mov al,c2
    sub al,32
    mov c2,al

    mov al,c3
    sub al,32
    mov c3,al

    ;print msg4
    mov ah,9h
    lea dx,msg4
    int 21h
    mov dl,10
    mov ah,2h
    int 21h
    mov dl,13
    int 21h

    ;print in reverse order: c3, c2, c1 (each on new line)
    mov ah,2h
    mov dl,c3
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    mov dl,c2
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    mov dl,c1
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main


============================================================
Question 7: Digit + special character, displayed together in same order (e.g. 5@)
============================================================
.model small
.stack 100h
.data

msg1 db "Enter a single digit: $"
msg2 db "Enter a special character: $"
msg3 db "Output: $"

numc db ?
specc db ?

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h
    mov ah,1h
    int 21h
    mov numc,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h
    mov ah,1h
    int 21h
    mov specc,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg3
    mov ah,9h
    lea dx,msg3
    int 21h

    ;print in same order: digit then special char
    mov ah,2h
    mov dl,numc
    int 21h
    mov dl,specc
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main


============================================================
Question 8: Special character + digit, displayed in reverse order (e.g. #,8 -> 8#)
============================================================
.model small
.stack 100h
.data

msg1 db "Enter a special character: $"
msg2 db "Enter a single digit: $"
msg3 db "Output: $"

specc db ?
numc db ?

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h
    mov ah,1h
    int 21h
    mov specc,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h
    mov ah,1h
    int 21h
    mov numc,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg3
    mov ah,9h
    lea dx,msg3
    int 21h

    ;print in reverse order: digit then special char
    mov ah,2h
    mov dl,numc
    int 21h
    mov dl,specc
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main


============================================================
Question 9: Uppercase, lowercase, digit -> print lowercase, uppercase, digit (e.g. A,b,7 -> a, B, 7)
============================================================
.model small
.stack 100h
.data

msg1 db "Enter an uppercase letter: $"
msg2 db "Enter a lowercase letter: $"
msg3 db "Enter a single digit: $"
msg4 db "Output: $"
sep  db ", $"

upc db ?
lowc db ?
numc db ?

.code
main proc
    mov ax,@data
    mov ds,ax

    ;print msg1
    mov ah,9h
    lea dx,msg1
    int 21h
    mov ah,1h
    int 21h
    mov upc,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg2
    mov ah,9h
    lea dx,msg2
    int 21h
    mov ah,1h
    int 21h
    mov lowc,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;print msg3
    mov ah,9h
    lea dx,msg3
    int 21h
    mov ah,1h
    int 21h
    mov numc,al

    mov ah,2h
    mov dl,10
    int 21h
    mov dl,13
    int 21h
    mov dl,10
    int 21h
    mov dl,13
    int 21h

    ;convert uppercase -> lowercase
    mov al,upc
    add al,32
    mov upc,al

    ;convert lowercase -> uppercase
    mov al,lowc
    sub al,32
    mov lowc,al

    ;print msg4
    mov ah,9h
    lea dx,msg4
    int 21h

    ;print: lowercase(from upc), ", ", uppercase(from lowc), ", ", digit
    mov ah,2h
    mov dl,upc
    int 21h

    mov ah,9h
    lea dx,sep
    int 21h

    mov ah,2h
    mov dl,lowc
    int 21h

    mov ah,9h
    lea dx,sep
    int 21h

    mov ah,2h
    mov dl,numc
    int 21h

    ;exit
    mov ah,4ch
    int 21h
main endp
end main