程序代码：

#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
void reverse(char *);
void main()
{
    char s1[100];
    gets(s1);
    reverse(s1);
    return ;
}
void reverse(char *s)
{
    char s1[100], s2[100];
    if(s[0] == '\0') {
        return  ;
    }
    else {
        sprintf(s1, "%c", putchar(toupper(s[0])));
        sprintf(s2, "%c", putchar(tolower(s[0])));
        reverse(&s[1]);
    }
}