CODEWITHSUNDEEP
assemblyx86-16
user130316
user130316

Reputation: 45

Intel 8086, infinite loop

I am trying to code a little application where a random number between 1-5 is generated using the system clock and the user has to guess the number and a message is displayed if the guess is correct.

Here is my code so far:

org 0x100


;Guess:
        MOV AH,2CH  ;DOS CALL TO GET SYSTEM CLOCK
        INT 21H     ;EXECUTE INTERRUPT 21H
        MOV AL,DL   ;RESULT RETURNED IN DL
        MOV AH,0    ;CLEAR THE HIGH BYTE
        MOV CL,20   ;GET DIVISOR
        DIV CL      ;DIVIDE VALUE IN AX BY VALUE IN CL
        MOV BL,AL   ;MOVE RESULT OF DIVISION INTO BL
        INC BL      ;INCREMENT BL TO GET NO BETWEEN 1-5

;Prompt:
        JMP START
        MSG DB "Enter a number between 1-5:$"

        START:  

        MOV DX, OFFSET MSG
        MOV AH, 09h 
        INT 21h

;User input:

        MOV AH, 1h  ;GET INPUT FROM THE KEYBOARD 
        INT 21h     ;THE CHARACTER INPUT IS STORED IN AL

;The Comparison: 

        ;MOV AX,AL   ;LOAD VALUE OF AL (USER INPUT)
        CMP AL,BL   ;COMPARE WITH BL

        JE Equal    ;IF EQUAL JUMP TO Equal
        JNE Not_Equal;IF NOT EQUAL JUMP TO Not_Equal        

        Equal:

        ABC DB "Your guess was correct!$"
        MOV DX, OFFSET ABC
        MOV AH, 09h 
        INT 21h        


        Not_Equal:

        DEF DB "Your guess was incorrect!$"
        MOV DX, OFFSET DEF
        MOV AH, 09h 
        INT 21h

My problem is that it just goes into an infinite loop.

Upvotes: 0

Views: 1120

Answers (1)

Michael
Michael

Reputation: 58507

You've got a few different problems in your code:

You can't mix code and data like this:

    ABC DB "Your guess was correct!$"
    MOV DX, OFFSET ABC

The CPU can't tell the difference between code and data and will try to execute whatever it encounters. Move the result strings to the same place where you've got the MSG string.

You're comparing numeric values with their corresponding ASCII characters:

    MOV AH, 1h  ;GET INPUT FROM THE KEYBOARD 
    INT 21h     ;THE CHARACTER INPUT IS STORED IN AL

If you enter the digit 2 in the terminal you'd get the character '2' (which is equal to 50) in AL. To successfully compare that against what you've got in BL you have to subtract '0' from AL.

You'll always print the "Your guess was incorrect" string. After the code that prints the "Your guess was correct" string there's no jump to skip the next print:

    ABC DB "Your guess was correct!$"
    MOV DX, OFFSET ABC
    MOV AH, 09h 
    INT 21h        

    ; Execution will simply continue here since there's nothing that changes the
    ; flow of execution.

    Not_Equal:

You're not terminating the program properly. At the end of your program you should add something like:

MOV AX,4C00h
INT 21h    ; Terminate with exit code 00h

Upvotes: 1

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