Assembly language case conversion

assume cs:codesg, ds:datasg
datasg segment
db 'BaSic'
db 'iNfOrMaTiOn'
datasg ends

codesg segment
start:	mov ax, datasg
		mov ds, ax
		mov bx, 0
		mov cx, 5
	  s:mov al, [bx]
		and al, 11011111B	;将al第5位设为0，变为大写字母
		mov [bx], al
		inc bx
		loop s
		
		mov bx, 5
		mov cx, 11
	 s0:mov al, [bx]
		or al, 001000000B	;将al第5位设为1，变为小写字母
		mov [BX], al
		inc bx
		loop s0
		
		mov ax, 4C00H
		int 21H
codesg ends
end start

;将每行第三个字母变为大写
assume cs:codesg, ds:datasg

datasg segment
	db '1. file         '
	db '2. edit         '
	db '3. search       '
	db '4. view         '
	db '5. option       '
	db '6. help         '
datasg ends

codesg segment
start:	mov ax, datasg
		mov ds, ax
		mov bx, 0
		mov cx, 6
	  s:mov al, [bx+3]
		and al, 11011111B	;变为大写字母
		mov [bx+3], al
		add bx, 16
		loop s
		
		mov ax, 4c00H
		int 21H
codesg ends
end start