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Hi everyone!  I'm having a bit of difficulty with making a program for a class. 
We have to use Euclid's algorithm for find the HCF (Highest Common Factor) for two multi-digit numbers.
The program has to prompt the user for the two inputs, then waits till the user presses enter to proceed.

The code that I have is for 1-digit, and doesn't wait for an enter key.


Here is my code so far.

.model small
.stack 200h
.data
 welcome db 'Henry' 0842', 0Ah, 0Dh, 'Euclids Algorithm', 0Ah, 0Dh, '$'
 prompt2  db 0Ah, 0Dh, 'Please type the first integer $'
 prompt3  db 0Ah, 0Dh, 'Please type the second integer $'
 prompt4  db 0Ah, 0Dh, 'The HCF is $'
 goodbye  db 0Ah, 0Dh, 'quiting now$'
.code
 
 mov dx, @data
 mov ds, dx
 
 mov dx, offset welcome 
 mov ah, 9d  
 int 21h   
 
 ;begin algorithm by reading in two 1-digit integers
 ;print the prompt first, using BIOS code '9d'
 mov dx, offset prompt2
 mov ah, 9d
 int  21h
 
 ;now get the keystroke
 mov ah, 1d  ;BIOS code for read a keystroke
 int 21h  ;invoke BIOS, ASCII code will be in register 'al' after this command
 ;save the keystroke in register 'cl'
 ;after we get the integer value from the ASCII code
 ;by subtracting hex 30 from the ASCII code value
 sub al, 30h
 mov cl,al
 
 ;now read the second integer as above
 ;first print the prompt using BIOS code '1d'
 mov dx, offset prompt3 ;set the offset for DS::DX
 mov ah, 9d  ;set BIOS code
 int 21h  ;invoke BIOS
 
 mov ah, 1d  ;BIOS code for read a keystroke
 int 21h  ;invoke BIOS, ASCII code will be in register 'al' after this command
 sub ah, 30h
 ; we now have two integers, actual values not ASCII codes, one in 'cl' and the other in 'al'
 

repeat: 
 cmp cl, al  ;compare the two integers
 jz print_and_exit ;print the result and return control to operating system
 ;if here, the two numbers were **NOT** the same
 ;note that the flags are still set from the compare statement, but it's probably wise to do another
 ;one in case we change or edit the file.
 cmp cl, al
 jg greater ;test to see if cl > al, and if it is, jump to label 'greater'
 ;OK, so if we get to here, cl **must** be less than (<) al
 sub al, cl  ;diminish 'al' by 'cl'
 jmp repeat ;go round the loop until the variables become equal
 
greater:
 ;if we get here, it was shown that cl > al, so diminish 'cl'
 sub cl, al
 jmp repeat ;go round the loop until the variables become equal
 

print_and_exit:
 ;there's only one way to get here and that's when the integers are equal
 ;so print and then we're done.
 
 ;first the prompt
 mov dx, offset prompt4
 mov ah, 9d ;BIOS code for print a string
 int 21h
 
 ;last, the actual result
 mov ah, 2d ;BIOS code for print to screen
 ;character's ASCII code must be in 'dl' for this to work
 mov dl, cl ;starting to print 'cl's value
 add dl, 30h ;convert value to ASCII code
 int 21h

mov dx, offset goodbye
mov ah, 9d
int 21h
 
 mov ah, 4ch ;BIOS code for exit/quit
 int  21h
 
end

My teacher gave me a hint



Can anyone lead me in the right direction?  I've looked in a few books but they are not really helping. 
I'm using TASM that runs in ms-dos from windows to compile and run this.

Thanks a lot!