rot13.c File Reference

ROT13 is a simple letter substitution cipher that replaces a letter with the 13th letter after it in the alphabet. More...

#include <stdio.h>
#include <string.h>
#include <assert.h>

Include dependency graph for rot13.c:

Functions
void	rot13 (char *s)
	for IO operations More...
static void	test ()
	Self-test implementations. More...
int	main ()
	Main function. More...

Detailed Description

ROT13 is a simple letter substitution cipher that replaces a letter with the 13th letter after it in the alphabet.

ROT13 transforms a piece of text by examining its alphabetic characters and replacing each one with the letter 13 places further along in the alphabet, wrapping back to the beginning if necessary. A becomes N, B becomes O, and so on up to M, which becomes Z, then the sequence continues at the beginning of the alphabet: N becomes A, O becomes B, and so on to Z, which becomes M.

Author

Jeremias Moreira Gomes

Function Documentation

main()

int main

(

void

)

Main function.

Returns

0 on exit

           {
    test();  // run self-test implementations
    return 0;
}

Here is the call graph for this function:

rot13()

void rot13

(

char *

s

)

for IO operations

for string operations for assert

Apply the ROT13 cipher

Parameters

s	contains the string to be processed

                    {
    for (int i = 0; s[i]; i++) {
        if (s[i] >= 'A' && s[i] <= 'Z') {
            s[i] = 'A' + ((s[i] - 'A' + 13) % 26);
        } else if (s[i] >= 'a' && s[i] <= 'z') {
            s[i] = 'a' + ((s[i] - 'a' + 13) % 26);
        }
    } 
}

test()

static void test ( void  )

static

Self-test implementations.

Returns

void

                   {
    char test_01[] = "The more I C, the less I see.";
    rot13(test_01);
    assert(strcmp(test_01, "Gur zber V P, gur yrff V frr.") == 0);
 
    char test_02[] = "Which witch switched the Swiss wristwatches?";
    rot13(test_02);
    assert(strcmp(test_02, "Juvpu jvgpu fjvgpurq gur Fjvff jevfgjngpurf?") == 0);
 
    char test_03[] = "Juvpu jvgpu fjvgpurq gur Fjvff jevfgjngpurf?";
    rot13(test_03);
    assert(strcmp(test_03, "Which witch switched the Swiss wristwatches?") == 0);
 
    printf("All tests have successfully passed!\n");
}

Here is the call graph for this function: