11. Program to Finding Multiples of K in Assembly Language using Visual Studio

Chapter 5

Procedures

Assembly Language Programming Exercise

Problem # 11:

In a byte array of size N, write a procedure that finds all multiples of K that are less than N. Initialize the array to all zeros at the beginning of the program, and then whenever a multiple is found, set the corresponding array element to 1. Your procedure must save and restore any registers it modifies. Call your procedure  twice, with K = 2, and again with K = 3. Let N equal to 50. Run your program in the debugger and verify that the array values were set correctly.

Solution:

.386
.model flat,stdcall
.stack 4096
ExitProcess PROTO, dwExitCode:DWORD

N = 50
.data
array BYTE N DUP(0)
K DWORD ?
.code
main PROC

    mov K, 2
    call multiplesOfK

    ;    re-initialize the array to zero
    MOV ECX, N
    L2:
        MOV BYTE PTR [ESI], 0
        ADD ESI, TYPE array
    LOOP L2
    mov K, 3
    call multiplesOfK

INVOKE ExitProcess,0
main ENDP

multiplesOfK PROC
    ; save all registers
    push ECX
    push ESI
    push EBX
    push EDX

    MOV ESI, OFFSET array
    MOV ECX, N        ; loop thorugh array
    MOV EDX, 1        ; compare array index 1 to 50
    MOV EBX, K        ; multiple of K
    L1:
        CMP EBX, EDX
        jne next

        ; multiple found
        MOV BYTE PTR [ESI], 1
        ADD EBX, K    ; next multiple of K

        next:
        INC EDX
        ADD ESI, TYPE array
    Loop L1

    ; retrieve all registers
    pop EDX
    pop EBX
    pop ESI
    pop ECX
    ret
multiplesOfK ENDP
END main

Let me know in the comment section if you have any question.

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