ex7_1.asm

x86汇编程序。 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

;The first method

.model small

dis_str macro x
    lea dx, x
    mov ah, 09h
    int 21h
endm

.data
    
    prompt db 'Please enter the string:', '$'
    ;the initial value is set to '$', so as to display string
    in_str db 100, ?, 100 DUP('$')  
    temp_str db 100 DUP('$')
    result1 db 'The initial string:', '$'
    result2 db 'The lowercase string:', '$'
    result3 db 'The uppercase string:', '$'
    result4 db 'The mutual exchanged string:', '$'

.code
.startup
 
    mov ax, @data
    mov ds, ax
    
    dis_str prompt   ;显示提示信息
    
    call input       ;调用输入字符串函数
    call crlf 
    call crlf 
    
    dis_str result1     ;显示原始字符串
    dis_str in_str+2 
    call crlf 
    call crlf 
    
    call upper_to_lower ;调用把大写字母转换为小写字母的函数
    
    dis_str result2     ;显示转换结果
    dis_str temp_str
    call crlf  
    call crlf 
    
    call lower_to_upper ;调用把小写字母转换为大写字母的函数
    
    dis_str result3     ;显示转换结果
    dis_str temp_str
    call crlf 
    call crlf  
    
    call mutual_convert ;调用把小写字母转换为大写字母的函数
    
    dis_str result4    ;显示转换结果
    dis_str temp_str
    call crlf
    call crlf   
    
.exit 0

;------------------------------------
input proc near
          
    push dx
    push ax
    
    lea dx, in_str
    mov ah, 0ah
    int 21h  
    
    pop ax
    pop dx
    
    ret   
              
input endp 

;------------------------------------------  
;换行
crlf proc near
    push dx
    push ax
    
    mov ah, 02h
    mov dl, 0dh
    int 21h
    
    mov ah, 02h
    mov dl, 0ah
    int 21h
    
    pop ax
    pop dx
    
    ret
crlf endp  
;------------------------------------------- 
upper_to_lower proc near
    push cx
    push si
    push bx

    ;set the counter
    mov cl, in_str + 1
    mov ch, 0
    
    mov si, 2
    
again1:
    
    ;只要处理A--Z的字符
    mov bl, in_str[si]
    cmp bl, 'A'  
    jb continue1
    cmp bl, 'Z'
    jb to_lower1
    jmp continue1
    
to_lower1:
    add bl, 20h
    
continue1:
    mov temp_str[si - 2], bl
    inc si
    loop again1
    
    pop bx
    pop si
    pop cx
    
    ret 
    
upper_to_lower endp
;----------------------------------
lower_to_upper proc near
    push cx
    push si
    push bx

    ;set the counter
    mov cl, in_str + 1
    mov ch, 0
    
    mov si, 2
    
again2:
    
    ;只要处理a--z的字符
    mov bl, in_str[si]
    cmp bl, 'a'  
    jb continue2
    cmp bl, 'z'
    jb to_upper2
    jmp continue2
    
to_upper2:
    sub bl, 20h
    
continue2:
    mov temp_str[si - 2], bl
    inc si
    loop again2
    
    pop bx
    pop si
    pop cx
    
    ret 
    
lower_to_upper endp 
;----------------------------------
mutual_convert proc near
    push cx
    push si
    push bx

    ;set the counter
    mov cl, in_str + 1
    mov ch, 0
    
    mov si, 2
    
again3:
    mov bl, in_str[si]
    cmp bl, 'A'  
    jb continue3
    cmp bl, 'Z'
    jb to_lower3
    cmp bl, 'a'
    jb continue3
    cmp bl, 'z'
    jb to_upper3
    jmp continue3 
    
to_lower3:
    add bl, 20h
    jmp continue3
    
to_upper3:
    sub bl, 20h
    
continue3:
    mov temp_str[si - 2], bl
    inc si
    loop again3
    
    pop bx
    pop si
    pop cx
    
    ret 
    
mutual_convert endp

end