Technolocus: A Program for Multiplication of 2 Numbers

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This program multiplies two digits supplied by the user as input. Then it displays the product as two decimal digit number. All the explanations of the instructions written here are supplied as comments.



data SEGMENT
    msg1 DB 'Enter a number: $'
    msg2 DB 0ah,0dh,'Enter another number: $'
    msg3 DB 0ah,0dh,'The product is: $'
    n1 DB ?
    n2 DB ?
    result DB ?
    ten DB 10
ENDS 

code SEGMENT 

start:
    MOV AX,data ;Initializes data segment 
    MOV DS,AX 

    print MACRO msg       ;Defines a macro 'print' 
        MOV AH,09h        ;Prints the string whose starting 
        MOV DX,OFFSET msg ;offset is stored in DX 
        INT 21h
    ENDM
    print msg1  ;Prints message and  
    MOV AH,01h  ;Gets the first digit 
    INT 21h
    SUB AL,'0'  ;Derives the true binary value 

    MOV n1,AL   ;Stores the value into variable n1 
    print msg2  ;Prints message and  
    MOV AH,01h  ;Gets the second digit 
    INT 21h 

    SUB AL,'0'      ;Calculates the true binary value 
    MUL n1          ;Multiply it with n1  
    MOV result,AL         

    print msg3
    MOV AL,result  ;Brings result in AL 
    MOV AH,0       ;Clears AH 

    DIV ten        ;If the result is not valid BCD 
    MOV DL,AL      ;divide the result by 10 to get  
    MOV CL,AL      ;the first digit and stores it in DL and CL 

    ADD DL,'0'     ;Get the ASCII code 
    MOV AH,02h
    INT 21h        ;Prints the first digit of product 

    MOV AL,CL      ;Mov the first digit to AL 
    MUL ten        ;Multiply it by 10 
    SUB result,AL  ;get the second digit  

    XCHG DL,result ;stores second digit in DL 
    ADD DL,'0'     ;Get the ASCII value 
    MOV AH,02h
    INT 21h        ;Prints the character 

    xit:
    MOV AH,4ch     ;Exits to the  
    INT 21h        ;Operating System 
ENDS
END start