======Trimethius' Tableau======

e = (t+x) - 26 [(t+x)/26] Where [] is the floor function.

<code c>
/*Encrypt using Trimethius' Tableau*/
#include <stdio.h>

int
main (int argc, char *argv[])
{

  int x, c;
  char s[256];
  strncpy(s,argv[1],255);
  char *alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ\0";
  for (x = 0; x < strlen (s); x++)
    printf ("[%c]", s[x]);
  printf ("\n");
  for (x = 0; x < strlen (s); x++)
    {
      c = ((int) s[x] - 65 + x) % 26;
      printf ("[%c]%d", alpha[c], c);
    }
}

/* Decrypt */

#include <stdio.h>

int
main (int argc, char *argv[])
{

  int x, c;
  char s[256];
  strncpy(s,argv[1],255);
  char *alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ\0";
  for (x = 0; x < strlen (s); x++)
    printf ("[%c]", s[x]);
  printf ("\n");
  for (x = 0; x < strlen (s); x++)
    {
      c = ((int) s[x] - 65 - x);
      if (c < 0) c = c+26;
      printf ("%c", alpha[c],c);
    }
printf("\n");
}


/*Encrypt with key as CIPHER*/
#include <stdio.h>

int
main (int argc, char *argv[])
{

  int x, c;
  char s[256];
  char *pass = "CIPHER\0";
  strncpy(s,argv[1],255);

  char *alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ\0";
  for (x = 0; x < strlen (s); x++)
    printf ("%c", s[x]);
  printf ("\n");
  for (x = 0; x < strlen (s); x++)
    {
      c = (((int) s[x] - 65 + (int) (pass[x % strlen(pass)] - 65))) % 26;
      printf ("%c", alpha[c]);
    }
}
</code>