TITLE Program Template     (template.asm)

; Author: Roger
; Assignment Number: demo                Due Date:
; Description: This program gets two integers, and calculate the
;				summation from the lower to the upper. 
; All variables are global ... no parameter passing 
; no data validation

INCLUDE Irvine32.inc

; (insert constant definitions here)

.data
	rule1	BYTE	"Enter a lower and upper limit, and I'll show: ",0
	rule2	BYTE	"the summation of ints from lower to upper.", 0

	a		DWORD	?		;lower 
	b		DWORD	?		;upper
	sum		DWORD	?		;sum of lower + lower +1 .... upper 

	out1	BYTE	"The summation from ",0
	out2	BYTE	" to ", 0
	out3	BYTE	" is: ", 0

	prompt1 BYTE	"Enter a lower limit: ", 0
	prompt2	BYTE	"Enter a upper limit: ", 0


; (insert variable definitions here)

.code
main PROC
	call	intro
	call	getData
	call	calculate
	call	showResults


	exit	; exit to operating system
main ENDP



; Procedure to introduce the program.
; receives: none
; returns: none
; preconditions: none 
; registers changed: edx
intro	PROC
	mov		edx, OFFSET rule1 
	call	WriteString
	call	Crlf

	mov		edx, OFFSET rule2 
	call	WriteString
	call	Crlf
	call	Crlf

	ret
intro	ENDP



;Procedure to get values for a and b from the user.
;receives: none
;returns: store user inputs (low & upper) into globals (a & b)
;preconditions: none
;registers changed: edx, eax
getData		PROC
	mov		edx, OFFSET prompt1 
	call	WriteString
	call	ReadInt
	mov		a, eax

	mov		edx, OFFSET prompt2 
	call	WriteString
	call	ReadInt
	mov		b, eax

	ret
getData ENDP



; Procedure to calculate the summation of integers from a to b.
; receives: a, b, sum, globals
; returns: global sum = a + a+1 + a+2 .... + b
; preconditions: a <= b
; registers changed : eax, ebx, ecx
calculate	PROC
	mov		eax, 0	;accum
	mov		ebx, a	

	;iterations: ecx = b-a+1
	mov		ecx, b
	sub		ecx, a
	inc		ecx

top:
	add		eax, ebx
	inc		ebx
	loop	top

	mov		sum, eax	

	ret
calculate	ENDP



; Procedure to display the results(a, b, and sum)
; receives: none, a, b, sum are globals
; returns: none
; preconditions: sum has been calculated  
; registers changed : eax, edx
showResults		PROC
	mov		edx, OFFSET out1 
	call	WriteString
	mov		eax, a
	call	WriteDec
	mov		edx, OFFSET out2 
	call	WriteString
	mov		eax, b
	call	WriteDec
	mov		edx, OFFSET out3 
	call	WriteString
	mov		eax, sum
	call	WriteDec
	call	Crlf

	ret
showResults		ENDP
	


END main