汇编程序18：利用and和or指令变换大小写

 assume cs:code,ds:data
 //and指令使某位变0,or指令使某位变1
 data segment
     db 'BaSic','iNfOrMaTiOn' //db指令:定义字节数据,与dw指令:定义字数据
 data ends

 code segment
     start:
           mov ax,data
           mov ds,ax
           mov bx,
           mov cx,
         s:
           mov al,[bx]
           and al,11011111B
           mov [bx],al
           inc bx
           loop s
           mov bx,
           mov cx,
        s0:
           mov al,[bx]
           or al,00100000B
           mov [bx],al
           inc bx
           loop s0
     mov ax,4c00h
     int 21h
 code ends

 end start