Program that reads a character from keyboard and displays next five and previous five characters.

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UNIVERSITY OF THE PUNJAB

Third Semester 2016

Examination: B.S. 4 Years Programme 

Paper: Computer Organization and Assembly Language

Course Code: IT-203 / 21402

Question # 3:

Write an assembly language program that reads a character from keyboard and displays next five and previous five characters. If user enters 'a' the next five letters will be b, c, d, e, f and previous letters will be z, y, x, w, v.

Solution:

INCLUDE Irvine32.inc

.data
msg BYTE "Enter an alphabet : ",0
error BYTE "Wrong Input!, Please enter an alphabet : ",0
input BYTE ?
.code
main PROC
    mov edx, offset msg
    call WriteString
    call ReadChar
    call ValidateInput
    call WriteChar
    mov input, al

    mov ecx, 5
    l1:
        inc al
        .IF(al>'z')
            mov al, 'a'
        .ENDIF
        call crlf
        call WriteChar
    loop l1

    call crlf
    mov al, input
    mov ecx, 5
    l2:
        dec al
        .IF(al<'a')
            mov al, 'z'
        .ENDIF
        call crlf
        call WriteChar
    loop l2

quit:
    call crlf
    call WaitMsg
    exit

main ENDP

ValidateInput PROC
    validate:
        .IF(al >= 'a' && al <= 'z')
            jmp quit
        .ENDIF
    BadInput:
        mov edx, offset error
        call WriteString
        call ReadChar
        jmp validate
    quit:
        ret
ValidateInput ENDP

END main

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