Help~!~

Hey guys. I'm making an encoding tool for messaging but the problem is, I don't know how to change the letters in the inputed message and I'm too lazy to look it up.... I just started it like 2 min ago and here's my code so far:

Code:

#include <iostream.h>
#include <stdlib.h>

int main()
{
      int wtd;
      int en;
      int randnm;
      char messagete['500'];
      sao:
      cout<<"1- Decode   2- Encode"<<endl;
      cin>>wtd;
      if(wtd == 2) {
      cout<<"What message would you like to encode? Max: 500 letters + spaces!"<<endl;
      cin>>messagete;
      randnm = rand();
      messagete = messagete + randnm;
      cout<<"The encoded message is:  ||| " << messagete << " ||| and the secret number is " << randnm <<endl;
      } else if(wtd == 1) {

      }
      goto sao;
      system("PAUSE");
      return 0;
}

basically it generates a random number, changes the message depending on the number (for now increases each letter like it was a number), and gives the person the encrypted message and the secret number which changes it back.

>>I'm too lazy to look it up<<

thats your problem...if you feel that way, at least don't state it in your posts - put some effort in what you do. I hope that no one here gives you the answer now. Good thing for you that there are members here that are much more forgiving than I am.

maybe lazy was a wrong word. busy is more of what I mean

we're all busy

Hmm.. I wont give you a complete answer yet.. but I will do this..

1. Use standard headers.

Code:

#include <iostream>
// not <iostream.h>

//add
using namespace std;
// so you wont have to put std:: before cout/cin
// do a search here and you'll see what it is about.

2.
Goto.. is a no-no..

put that code into a function and do a loop to call it.

Code:

void Function ()
{

    // code here

}

int main ()
{

    char choice;

    while ( choice != 'q' ) {

        Function (); // This will do the code in "Function"        

        cout << "q to quit" << endl;
        cin  >> choice;

    }

    return 0;

}

3.

Code:

char message ['500']; 
// no

// its
char message [500];

I dont even think that will compile.

4.
you dont need stdlib in there.

cin.get () will wait for the user to hit enter. system () commands are not really good.

But fix up these problems then post again.

Also read the faq section

http://faq.cprogramming.com/cgi-bin/smartfaq.cgi

lots of good info.

>>Goto.. is a no-no..<<

lol, I haven't even looked at his code...hehe. goto is powerfull if you know how to use it... gotta love directed breaks in java

Wasnt there a faq entry about goto? I looked but didnt see it.

ty for that info but u still haven't solven my problem. I need to change the message depending on the random number

Go look at Axon's first post and take a wild flying guess why that is. If you know how to look it up, look it up. I am, as you say, too busy to help people who can't even think.

Originally Posted by axon

>>Goto.. is a no-no..<<

lol, I haven't even looked at his code...hehe. goto is powerfull if you know how to use it... gotta love directed breaks in java

goto is powerful even if you don't know how to use it... powerful at turning your program into mush and confusing the hell out of you

>>ty for that info but u still haven't solven my problem.
Wrong wording again, I suppose What you meant to say was, "ty for that info but that still doesn't help me to solve my problem."

Your code won't work, simply because wrapping is undefined for characters and rand() will almost certainly return a value that will overflow the char datatype. One solution is to store the result of rand() + (the char) in an unsigned long, use the mod operator (%) and some arithmetic to bring it down into the -127 to 128 range (or whatever it is), and then convert back to char. And you'll need to find some way to store each random number too, and then find a way to de-'encrypt' each character. I'll leave that up to you.

**EDIT**
If you're so 'busy' that you can't figure out something this simple for yourself, I don't see why you even started on this program. If you don't have the time to write it, why bother? It's not like it's useful or anything anyway.

Ok look

For a random number to work like you want it you have to do something like so.

Code:

// seed the random function
srand ( time ( NULL ) );

// use the modulous operator to get a number between 0 and MAX_NUMBER
your_value = rand () % MAX_NUMBER;

That is how you do a random number.

So to scramble a message.

Code:

char ScrambleChar ( char the_char )
{

     char value = rand () % 20;

     return the_char + value;

}

Something like that is probably what your looking for. Althogh if you plan on decrypting it. random numbers like this is not a good idea.

I showed you this code so you will realize even though I have given you the answer, your program will still not work right without the above info. We arent just mean people who dont want to help. Actually we gave you more help then you asked for

>>rand () % MAX_NUMBER
That would give a number from 0 to MAX_NUMBER - 1

Code:

//Encode
int key = rand();
unsigned long newVal = theChar + key;
newVal %= 256;
char convertedChar = newVal - 128;
 
//Decode:
newVal = (convertedChar + 128) << 24;
newVal -= key;
theChar = newVal % 256;

Originally Posted by Hunter2

>>rand () % MAX_NUMBER
That would give a number from 0 to MAX_NUMBER - 1

Code:

//Encode
int key = rand();
unsigned long newVal = theChar + key;
newVal %= 256;
char convertedChar = newVal - 128;
 
//Decode:
newVal = (convertedChar + 128) << 24;
newVal -= key;
theChar = newVal % 256;

Yeah thats why I said "between" but then that might not have ben good wording since 0 is included.

And I was under the assumption that he would eventually want to encode the message out to a file and then decode it back in. And in that case a random number wouldnt really work.

>>Yeah thats why I said "between" but then that might not have ben good wording since 0 is included.
*checks the post again* Oops

>>And in that case a random number wouldnt really work.
>and the secret number which changes it back.
I imagine that means that the random number is saved to the file? Actually, I was thinking along the lines of a one-key-per-character format, where each character gets its own random number. Still, you're right - not very secure