I want to show "Hello World" once the user entered the correct password, but if the password is incorrect the program will prompt for Yes(Y)/No(N), if the user entered Yes(Y), the program will give 3 chances to the user to show the "Hello World" and if the user entered the No(N), the program will exit. My problem is that, every time I select Yes(Y), the program keeps looping, it just end if I entered No(N),
Here is the my code(I've skipped some parts)
...
org 0100h
.code
mov ah, @data
mov ds, ah
mov cx, 3
pool:
dec cx
jz full ;jump if equal to zero seems of no effect, the loop is still counting
dsply:
<codes here are for requesting and comparing the password>
...
...
...
cmp bl, al
jne errr
cmp cl, al
jmp welc
errr:
mov ah, 9
lea dx, pmpt ; Displays whether the Yes(Y)/No(N)
int 21h
mov ah, 1
mov cl, al
int 21h
cmp cl, 'Y'
je dsply
cmp cl, 'N'
je endmain
loop pool
full:
mov ah, 9
lea dx, att ;att will display You've Exceeded
int 21h
jmp endmain
welc:
mov ah, 9
lea dx, hw ; Displaying Hello World
int 21h
jmp endmain
endmain:
mov ah, 4ch
int 21h
end main
I don't know if this codes are right, I don't have the copy of my code right now, and also, I'm sorry if my code and explanation of the problem look stupid, but if anyone could please to help, it would be great, and more great if you could give me your another idea :)
errr: mov ah, 9 lea dx, pmpt ; Displays whether the Yes(Y)/No(N) int 21h mov ah, 1 mov cl, al int 21h
You don't put your input in the CL register at all!
You need to move the mov cl, al instruction below the int 21h instruction.
mov ah, @data mov ds, ah
I don't see how this can work. You should use a 16-bit register here.
mov ax, @data
mov ds, ax
cmp cl, al jmp welc
Most probably this unconditional jmp is meant to become the conditional jne.
pool: dec cx jz full
You don't need this dec cx and jz full at the top of your loop. The loop pool instruction further below already does what is needed. (Observed by Sami Kuhmonen).
However...
since the loop instruction is slow (Observed by Peter Cordes) you should avoid using it and replace it with code similar to the redundant instructions you had at the top of your loop.
But wait, there's one more thing wrong! Your loop uses the CX register as its iteration counter, but at the same time the code within the body of the loop uses this same CX register for other purposes. This inevitably leads to problems! You need to be careful with how you use these registers.
This is a solution:
mov cx, 3
pool:
push cx ;(1) Save the iteration counter on the stack
dsply:
...
<codes here are for requesting and comparing the password>
...
pop cx ;(1) Restore the iteration counter
dec cx
jnz pool
full:
mov ah, 9
cmp cl, 'Y' je dsply cmp cl, 'N' je endmain
Once you got your program working, you'll have a potential problem here. What will happen when the user types in a small "y" or a small "n" ?
The program won't recognize it!
It would be best to capitalize the input:
and cl, 11011111b
cmp cl, 'Y'
je dsply
cmp cl, 'N'
je endmain
Please use the DOS API as it is intended to be used. The TerminateWithReturnCode function does expect a return code in the AL register. It's a real small effort to write:
mov ax, 4C00h ;Function number in AH, Return code in AL
int 21h