Subj : simple c/c++ programming question about encryption
To   : comp.programming
From : jagivens
Date : Mon Jul 04 2005 04:39 pm

Hi,

I have two identical programs that encrypt characters.  One is written
in C++, and it works, but the other one is written in C, and it does
not work.  I have copied the code below.  There is a problem somewhere
in the while loop in the C program.  It goes through the code one full
time (and updates the counter) before asking for user input - thus it
updates the counter twice for every one input.  Since I'm not so
familiar with C, can anyone explain this to me.  The same program works
perfectly with C++, which is why I don't understand this.  Any help
would be much appreciated.

Thanks,
JAG

============================== c program
====================================

#include <stdio.h>  // input, output
#define BASE 33
#define RANGE 93
main(){
char originalLetter;
char encryptedLetter;
int k;
int i;
int counter = 1;

// asks the user for the number of characters to encrypt
printf("How many characters would you like to encrypt?\n");
scanf("%d", &i);
printf("What is the shifting distance (less than 93!)?\n");
scanf("%d", &k);


while (counter <= i) {
   printf("Input a character: ");
   scanf("%c", &originalLetter);

   if(originalLetter >= '!' && originalLetter <= '~' && k < 93 && k >=
0){
     encryptedLetter = BASE+(originalLetter-BASE+k)%RANGE;/*the
calculation*/
     printf("The encrypted character is %c.\n", encryptedLetter);
/*Output */
   }
    counter = counter + 1;
}

}

========================================c++ program
=====================

#include <iostream>
#define BASE 33
#define RANGE 93
using namespace std;

int main()
{
char originalLetter;
char encryptedLetter;
int k;
int i;
int counter = 1;

// asks the user for the number of characters to encrypt
cout << "How many characters would you like to encrypt?\n";
cin >> i;
cout << "What is the shifting distance (less than 93!)?\n";
cin >> k;


while (counter <= i) {
   cout << "Input a character: \n";
   cin >> originalLetter;

   if(originalLetter >= '!' && originalLetter <= '~' && k < 93 && k >=
0){
     encryptedLetter = BASE+(originalLetter-BASE+k)%RANGE;/*the
calculation*/
     cout << "The encrypted character is " << encryptedLetter << "\n";
/*Output */
   } 
    counter = counter + 1;
}

}

.