程序代码：

void
reverse_string( char *str )
{
    char *last_char;
   
    for( last_char = str; *last_char != NUL; last_char++ )
        ;
    last_char--;

    while( str < last_char )
    {
        char temp;
       
        temp = *str;
        *str++ = *last_char;
        *last_char-- = temp;
    }
}

void
main()
{
    char *cpStr = "abcdefg";

    reverse_string( cpStr );

    while( *cpStr != NUL )
    {
        printf( "%c\n", *cpStr++ );
    }
}