TITLE               (SumUp1.asm)

; promt and read N and out: 1 + 2 + ... N
; Last update: 11/28/17
;

INCLUDE Irvine32.inc

.data
msg BYTE "Input N: ", 0
msg2 BYTE "ANS = ", 0

.code
main PROC
LBG:	
	MOV EDX, offset msg
	call WriteString

	; if N<0 then quit
	
	call ReadInt	; EAX = N

	CMP EAX, 0
	JLE EXT

	call sum		; call the precedure
	
	

	call crlf
	MOV EDX, offset msg2
	call WriteString

	call WriteDec

	call crlf
	call crlf
	
	JMP LBG
EXT:

	exit
main ENDP

sum PROC USES ECX EBX	; p.141
	; Pre-condition: 	EAX = N
	; Post-cond.:		EAX = 1+2 ..
	; PUSH ECX

	MOV ECX, EAX	; ECX = N
	MOV EAX, 0
	MOV EBX, 1
LP:
	ADD EAX, EBX	; EAX = 1+2+...
	INC EBX		; EBX ++
	
	LOOP LP

	; POP ECX
	RET
sum ENDP

END main