ctwo.asm

从键盘输入一个字符串,先把它原样显示一遍 然后将其中的小写字母转换为大写显示,再将其中的大写字母转换为小写显示,最后将其中的大小写字母互换显示.显示字符串的功能调用采用宏,大写转换,小写转换和大小写互

cmdenter MACRO 
                    mov ah ,02h
                    mov dl ,0dh
                    int 21h
                    mov dl ,0ah
                    int 21h
          ENDM
dispmsg	macro  message	;显示message字符串
	mov dx,offset message
	mov ah,9
	int 21h
	endm
dispmsg1 macro name,length
	local again,quit
	lea si,name+2
	mov cl,length
again:	cmp cl,0
				je quit
				mov dl,[si]
				mov ah,02
				int 21h
				dec cl
				inc si
				jmp again
	quit:
	endm
.model small
.stack
.data
input db 'input a string ',0dh,0ah,'$'
 sourstr db 50,0,50  dup(0)
 highstr db 50, 0,50 dup(0)
 lowstr db 50, 0,50 dup(0)
converstr db 50,0,50 dup(0)
.code
public sourstr,highstr,lowstr,converstr
extern contohigh:far, contolow:far, toconverse:far
.startup
dispmsg input
mov dx,offset sourstr
mov ah,0ah
int 21h
cmdenter
mov al,[sourstr+1]
mov [highstr+1],al
mov [lowstr+1],al
mov [converstr+1],al
dispmsg1 sourstr,al
cmdenter

call contohigh
dispmsg1 highstr,[highstr+1]
cmdenter

call contolow
dispmsg1 lowstr,[lowstr+1]
cmdenter
call toconverse
dispmsg1 converstr,[converstr+1]
.exit 0
end