程序代码：

#include <stdio.h>
int main(int argc, char *argv[])
{
    char str[0x7F];
    for(int i=0; i<0x7F; ++i)
        str[i] = i;
    for(int i='a'; i<'z'; ++i)
    {
        str[i] = i+1;
        str[i^0x20] = i^0x20+1;        
    }
    str['z'] = 'a';
    str['Z'] = 'A';
    while(putchar(str[getchar()]) != '\n')
        ;
    return 0;
}