TITLE Simple Procedure Practice... (ford1.asm)

; Permutations and combinations

INCLUDE Irvine32.inc

.data
sQueryStr BYTE "Enter the number of objects to choose from: ", 0
sChooseStr BYTE "Enter the number of objects to choose: ", 0
sInvalidInt BYTE "You have entered an invalid integer!" , 0
sError BYTE "Could not complete calculation!", 0
sResult BYTE "The result is: ", 0


.code
main PROC
    mov edx, OFFSET sQueryStr
    call WriteString
    call ReadInt
    jnc okay1
badInt:
    mov edx, OFFSET sInvalidInt
    call WriteString
    call crlf
    jmp myExit
okay1:
    push eax
    mov edx, OFFSET sChooseStr
    call WriteString
    call ReadInt
    jc badInt
    push eax
    call Calc
    jc ErrorInCalc
    mov edx, OFFSET sResult
    call WriteString
    call WriteInt 
    call crlf
    jmp myExit   
ErrorInCalc:
    mov edx, OFFSET sError
    call WriteString
    call crlf
myExit:
	exit
main ENDP

; Calc should compute the number of combinations one can choose n objects from a set of m objects
; It should handle unexpected inputs and print a suitable error message on meaningless 
; requests (like choosing 0 objects from 20, or 20 from 1). 
; It should not change any of the registers except eax, which should contain the final value
; It should not mindlessly pushad :) at the beginning of the code
; If the calculation cannot be carried out, it should print a meaningful error message, set
; the carry flag and return a value of 0 in eax. If the calculation is successful it should
; clear the carry flag
; You should manage the stack *without* masm macros (like USES or forms like dataPTR: PTR WORD)
; You may, however, use LOCAL.

Calc PROC
   ; Replace the following... enjoy.
   mov eax, 12345h	; Example code
L2:	ret
Calc ENDP

end Main