次程序经过调试通过，绝对可以使用，有不懂或是要EXE文件请发我邮件！
public info1,info2,bufa,bufb,buf,main,info0,info3
extrn change1:far,change2:far,change3:far,change4:far
data segment
info0 db 0ah,0dh,'this is the change of letter to leter:$'
info1 db 0ah,0dh,'please input string:$'
info2 db 0ah,0dh,'output string:$'
bufa db 81
db ?
db 80 dup (?)
bufb db 80 dup (?)
info3 db 0ah,0dh,'this is the change of digital to digital:',0ah,0dh,'$'
buf db 0dh,0ah,'the number is:0100101010001111b',0ah,0dh,'the result is:$'
data ends
stack segment stack
db 200 dup (?)
stack ends
code segment
main proc far
assume ds:data,cs:code,ss:stack
mov ax,data
mov ds,ax
disp macro m
lea dx,m
mov ah,9
int 21h
endm
call change1
call change2
disp info3
disp buf
call change3
call change4
ret
main endp
code ends
end