C/C++ Caesar Cipher on a .txt file?

BillyBob's Avatar, Join Date: Dec 2007
Newbie Member
Hi, How would I go about using the Caesar Cipher technique on a .txt file? E.g. shifting each letter by 3?

Here is my code?

#include <stdio.h>
#include <conio.h>

#define CNTRLZ 0x1A

char sourceFileName[] = "H:\\text.txt";
char commStreamName[] = "COM1";
FILE *commStream;
FILE *SouceFile;
char charToSend;
char ReadAccess[] = "r";
char WriteAccess[] = "w";
char errorMsg[] = "fail to open data file\n";
char fileopenflag[] = "r";
char EndOfFile[] = "EOF";

int main(void) {
FILE *fp;
FILE *dp;
int c;

if ((dp = fopen("COM1", "r")) == NULL) {
printf("fail to open COM port\n"); return 1;

if ((fp = fopen( sourceFileName, "w")) == NULL) {
printf("fail to open data file\n"); return 1;

while ((c = fgetc(fp )) != EOF) {
fputc( c, dp);


fputc('*', dp);
Any ideas where to start?

Last edited by shabbir; 16Dec2007 at 09:13.. Reason: Code block
Salem's Avatar, Join Date: Nov 2007
Ambitious contributor
Did you even pay any attention to your other thread, with the same code?
BillyBob's Avatar, Join Date: Dec 2007
Newbie Member
You weren't no help as usual.
shabbir's Avatar, Join Date: Jul 2004
Go4Expert Founder
Duplicate of C Encryption?? Adding Encryption To Text File?. Thread closed.

If you did not understand on that thread try responding what you could not understand instead of starting fresh.