TITLE DemoString     (demo6.asm)

; Author: Roger
; CS271	in-class demo        2/22/2022
; Description:  This program asks the user to enter a string,
;               and then displays the string in all caps.
;               Finally, the string is displayed backwards.

INCLUDE Irvine32.inc

MAXSIZE	= 100								; constant

.data
inString	BYTE		MAXSIZE DUP(?)		; User's string
outString	BYTE		MAXSIZE DUP(?)		; User's string capitalized
prompt1		BYTE		"Enter a string: ",0
sLength		DWORD		0

.code
main PROC
; Get user input:
	mov		edx, offset prompt1
	call	WriteString
	mov		edx, offset inString
	mov		ecx, MAXSIZE
	call	ReadString
	call	Crlf
	

	
; Set up the loop counter, put the string addresses in the source 
; and index registers, and clear the direction flag:

	mov		sLength, eax
	mov		ecx, eax
	mov		esi, offset inString
	mov		edi, offset outString

	cld
	

; Check each character to determine if it is a lower-case letter.
; If yes, change it to a capital letter.  Store all characters in
; the converted string:
; while inString[i] >= 97 && inString[i] <= 122  (97-'a', 122-'z', 65-'A', 90-'Z')

counter:
	lodsb			; mov al , [esi]    inc esi
	cmp	 al, 97
	jl	 notLC
	cmp	 al, 122
	jg	 notLC
	sub	 al, 32

notLC:
	stosb
	loop counter

	
; Display the converted string:
	mov		edx, offset outString
	call	WriteString
	call	Crlf

	
	
; Reverse the string
	mov		ecx, sLength
	mov		esi, offset inString
	add		esi, ecx
	dec		esi
	mov		edi, offset outString

reverse:
	std	
	lodsb

	cld
	stosb
	loop reverse


; Display reversed string
	mov		edx, offset outString
	call	WriteString
	call	Crlf

	
	
	exit			;exit to operating system
main ENDP

END main