Thread: Guessing the Password

Hey guys,
I am new to the forums and pretty average at c programming at the moment, but there is this one program that i just cant get to run and it is annoying the hell out of me. please help, any advice is greatly appreciated


Basically i am trying to get it to ask you to guess password and if you get it wrong it says try again, and if you get it right the program ends. I would like to add 3 choices to it as i learn more. i know this is the simplest program but I am determined to get it working, thanks

Code:

#include <stdio.h>
#include <stdlib.h>

int main()
{
  int pass;
  int guess;

  pass = 123;
  printf("Try and Guess My Password\n");
  printf("Password: %d ", guess);
  scanf("%d", guess);

  if (guess != pass) {
    printf("incorrect try again");
  } else {
    printf("You guessed it");
  }
  return 0;
}

I suggest you read up on scanf. You should be passing a pointer to guess, not guess itself.

I also STRONGLY suggest that you always compile with all warnings enabled. That would have picked up this and lots of other problems for you automatically. I assume you didn't notice you'd printed guess before you'd inputted it?

Well ofcouse it not going to work. You haven't read any value of the user for the variable guess have you? meaning the guess1 has a garbage value!

>I suggest you read up on scanf. You should be passing a pointer to guess, not guess itself.
What is means is, that scanf need the address of a variable to store the data. What you had was just the variable name. Which dosn't provide the address of a variable. Something like this

Code:

scanf("%d", &guess);

This provides the scanf with the address of the variable guess1 which allows it store the user entered data in the memory.

Just do this modification in your orginal code and you should have some progress.

ssharish

scanf can and will run amok if you let it. What happens if your user enters anything other than a digit? Once you've got your loop ironed out, try entering characters using scanf to see the little gremlins take control, and then mill over this. As for the wrong password, you'll want a loop. do-while is handy.

Code:

do {

   /* prompt for and read input */
   /* output message if wrong (if desired) */

} while(test condition is false);

In the future, use something like this website: scanf - C++ Reference to look up functions and see how they operate, what they should be given and what they should return (and, thus, what you should be CHECKING for them returning every time you use them.

Learning programming from one book is a horrendous waste of time and effort, especially if they don't have some equivalent function listing within them. Find yourself some google-able online resources so you can look up how things work and not have to treat entire swathes of the C standard library like some kind of black box with no documentation.

Even though I am still sort of new to the C language, I am still aware of scanf(), I suggest not using it. The error has occurred at your scanf() statement, you need to include an ampersand (&) to store an integer in memory *from what I know*. So the statement will now be scanf("%d", &guess);

Also for that bit how you wanted a limited amount of guesses, you would probably want to have a loop running with it set to loop through 3 times of the user trying to guess the password, if the condition is met then end the loop and if the condition is not met and the loop count is still less than 3 just increment the loop count.

Hope this helped you

Originally Posted by MyBlackSon

I am still aware of scanf(), I suggest not using it.

What do you suggest the OP use instead?

You do realise that you just advocated recreating a scanf equivalent to a user who doesn't understand that all they needed was an ampersand (&) and that didn't know what it was or did?

I'm not sure the advocation of avoiding scanf is entirely sensible anyway. About the only real problem with it (the examples linked are pretty minor and avoidable) is the "%s" format specifier being slightly insecure, which is easily avoided (don't use scanf with a %s for untrusted input). I think "recreating the wheel" of remaking scanf just because of that one entirely avoidable problem is a bit of overkill, where scanf's primary usage nowadays is in programming tutorials to receive input from the command line (which is a pretty unusual use scenario - I don't think there's much outside of ancient, well-catered-for uses of such stdin input nowadays) for which it does a pretty good job.

scanf is fine here, and unlikely to make it into any "modern" program at all, and asking beginner users who have trouble using it to recreate an equivalent with some even more underpowered tools is counter-productive. Personally, I think the OP should ignore the suggestion and just fix their original program.