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

BillyBob's Avatar
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
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.