I've wrote a program that takes a text file in as a string, and encrypts it, using my own, very weak, encryption key. The program works, as long as the text file contains only a single word, with no spaces. I'm assuming for some reason it doesn't like spaces. My code is as follows

Code:
#include <stdio.h>
#include <string.h>


int main (int argc, char *argv[])
{
  FILE *in;
  FILE *out;
  char buf[512];
  char secret[512];
  int x;
   
  in = fopen ( argv[1], "r" );
  out = fopen (argv[2], "w+" );

  if ( in == NULL ) {
    perror ( "Unable to open the file" );
  }

  /* Read a string */
  fread ( buf, 1, sizeof buf, in );
  printf ( "%s\n", buf );

  /*pre programm processesing and beautifying*/
  system("clear");
  printf("\n\n");


   for (x = 0; x < 512; x++) { //begin for loop
   switch(buf[x])
   {  //begin switch/case
   
   // encryption key hidden for security reasons

   }  //end switch/case
   }  //end for loop



  fprintf(out, "%s\n", secret);  
  fclose ( in );
  fclose (out);


  printf("%s\n", secret);



   printf("\n\n");
} //end main
If anyone could recommend any modifications, I'd appreciate it.
Michael