汇编语言功能字符串大小写转换实现实例详解

assume cs:code,ds:data
data segment
	db 'BaSiC'
	db 'InfoMaTion'
data ends
;------------------------------------
;做法一
code segment
start:	        mov ax,data
		mov ds,ax
		mov bx,0	;设置ds:bx指向数据段		
		mov cx,5	;对于第一个字符串进行循环转换
s:		mov al,ds:[bx]
		and al,11011111B  ;将字符的第五位转换成0，转换成大写字母
		mov ds:[bx],al
		inc bx
		loop s 
		mov bx,5	;指向第二个字符串
 		mov cx,11
s0：		mov al,ds:[bx]
		or al,00100000B	  ;将字符的第五位转换成1，转换成小写字母
		mov ds:[bx],al
		inc bx
		loop s 
		mov ax,4c00h
		int 21h
code ends
;------------------------------------
;做法二，改进版：利用bx+idata实现代码的简化
 
code segment
start:	        mov ax,data
		mov ds,ax
		mov bx,0
		mov cx,5
s:		mov al,ds:[bx]
		and al,11011111b
		mov ds:[bx],al
		mov al,ds:[bx+5]
		or al,00100000b
		mov ds:[bx+5],al
		inc bx
		loop s 
code ends
;------------------------------------
end start

assume cs:code,ds:data
data segment
	db '1. file         '
	db '2. edit         '
	db '3. search       '
data ends
code segment
start:	        mov ax,data
		mov ds,ax
		mov bx,0	;ds:bx指定数据段，同时bx作为定义行的变量 
		mov cx,3
s:		mov al,ds:[bx+3]	;3作为常量，定义第一个字母
		and al,11011111b
		mov ds:[bx+3],al
		add bx,16
		loop s 
		mov ax,4c00h
		int 21h
code ends
 
end

assume cs:code,ds:data,ss:stack
data segment
	db 'ibm             '
	db 'dec             '
	db 'vax             '
data ends 
;--------------------------------------------
;做法一
code segment
start:	        mov ax,data
		mov ds,ax
		mov bx,0 
		mov cx,3
s0:		mov dx,cx	;同时使用同一个变量进行循环，需要对外层循环的值保存
		mov si,0
		mov cx,3	;cx设置成内层循环的次数 
s:		mov al,ds:[bx+si]
		and al,11011111b
		mov ds:[bx+si],al
		inc si		
		loop s
 		add bx,16
		mov cx,dx	;用dx中存放的外层循环恢复外层循环的计数器
		loop s0
 		mov ax,4c00h
		int 21h
code ends 
;--------------------------------------------
;做法二，利用栈保存外层循环的值
stack segment
	dw 8 dup(0)		;利用栈段保存cx的值
stack ends
code segment
start:	        mov ax,stack
		mov ss,ax
		mov sp,16	;ss:sp指向栈段 
		mov ax,data
		mov ds,ax
		mov bx,0	;ds:bx指向数据段
 		mov cx,3
s0:		push cx
		mov si,0
		mov cx,3 
s:		mov al,ds:[bx+si]
		and al,11011111b
		mov ds:[bx+si],al
		inc si
		loop s 
		add bx,16
		pop cx
		loop s0
 		mov ax,4c00h
		int 21h
code ends
;-------------------------------------------- 
end start

assume cs:code,ds:data,ss:stack
data segment
	db '1. display      '
	db '2. brows        '
	db '3. replace      '
data ends
stack segment
	dw 8 dup(0)
stack ends 
code segment
start:	        mov ax,stack
		mov ss,ax
		mov sp,16 
		mov ax,data
		mov ds,ax
		mov bx,0 
		mov cx 3	;设置外层循环只有3行
s0:		push cx
		mov si,0
		mov cx,4	;设置内层循环只需4次 
s:		mov al,ds:[bx+si+3]		;设置需要改变的第一个字母
		and al,11011111b
		mov ds:[bx+si+3],al
		inc si
		loop s 
		add bx,16
		pop cx
		loop s0 
		mov ax,4c00h
		int 21h
code ends
 
end start

assume cs:code,ds:data
data segment
	db 'conversation'
data ends
 
code segment
start:	                mov ax,data
		        mov ds,ax
		        mov si,0		;ds:si指向字符串所在空间的首地址
		        mov cx,12		;cx存放字符串的长度
		        call capital
		        mov ax,4c00h
		        int 21h
 
capital:	        and byte ptr ds:[si],11011111b
			inc si
			loop capital
			ret
code ends
 
end start

assume cs:code,ds:data
data segment
	db 'conversation',0
data ends 
code segment
start:		        mov ax,data
			mov ds,ax
			mov si,0			;ds:si指向数据段的开始处 
			call capital
 			mov ax,4c00h
			int 21h 
capital:	        mov cl,ds:[si]		
			mov ch,0
			jcxz ok				;如果字符串为0，则会跳出循环
			and byte ptr ds:[si],11011111b
			inc si
			jmp short capital	        ;跳转实现循环 
ok:			ret				;结束循环 
code ends
end start

assume cs:code,ds:data,ss:stack
data segment
	db 'word',0
	db 'unix',0
	db 'wind',0
data ends
stack segment
	db 8 dup(0)
stack ends 
code segment
start:		        mov ax,data
			mov ds,ax
			mov bx,0 
			mov cx,3		;外循环实现
s:			mov si,bx
			call capital
			add bx,5		;内循环的实现
			loop s 
			mov ax,4c00h
			int 21h 
capital:	        push cx
			push si 
change:		        mov cl,ds:[si]
			mov ch,0
			jcxz ok
			and byte ptr ds:[si],11011111b
			inc si
			jmp short change 
ok:			pop si
			pop cx
			ret 
code ends
end