//===========================================================================
// Caesar Cipher with step of 13.  (ROT-13 encoding). 
//===========================================================================
// 
// Informatics 2C Computer Systems
// Coursework 1
// 
// Paul Jackson
// 10 Oct 2012

// Template for MIPS code

//---------------------------------------------------------------------------
// C definitions for SPIM system calls
//---------------------------------------------------------------------------
#include <stdio.h>

int read_char() { return getchar(); }
int read_int()
{
    int i;
    scanf("%i", &i);
    return i;
}
void read_string(char* s, int size) { fgets(s, size, stdin); }

void print_char(int c)     { putchar(c); }   
void print_int(int i)      { printf("%i", i); }
void print_string(char* s) { printf("%s", s); }

//---------------------------------------------------------------------------
// Global variables
//---------------------------------------------------------------------------
#define BUF_SIZE 40
char buf[BUF_SIZE];


//---------------------------------------------------------------------------
// MAIN function
//---------------------------------------------------------------------------
int main (void)
{
    print_string(" input: ");

    // Read input string into buf.
    // String stored in buf is always NUL ('\0') terminated.
    read_string(buf, BUF_SIZE);
    
    char* buf_p = buf;
    while (1) { 

        int c = *buf_p;
        if (c == '\0')  break;

        if ('a' <= c && c <= 'z') {
            c = c + 13;
            if (c > 'z') c = c - 26;
        }
        *buf_p = c;
        buf_p++;
    }

    print_string("\noutput: ");
    print_string(buf);
    print_string("\n");
    return 0;
}

//---------------------------------------------------------------------------
// End of file
//---------------------------------------------------------------------------