Another C question tonight

[imfrrreal]

I want to write a function that simulates an ATM operation.

If a user incorrectly enters their pin more than 3 times, I want to show an error.

This program is simple, so the only way the user can incorrectly enter a pin is if they enter less than four digits.

How would I write this function?

[Dave_Sinkula]

What have you tried?

[imfrrreal]

Basically What I'm doing ruling out entries that are less than 1000. It's not working. Maybe it's the way I link int getPin to the main.. I'm not sure

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

//Global Dec's
int getPin ();
void getReciept (void);
void menuChoose (void);

int main (void)
{
    //Local Dec's
    int attempts;
  
        
    printf("Welcome to Virtual Bank at West/n");
    attempts = getPin ();
    if (attempts <= 3)
    {
    getReciept();
    menuChoose();
}
    else
    system("pause");
    return 0;
}
    
//getPin

int getPin ()
{
    int pin;
    int attempts;
    printf("Please enter pin number: \n");

     if (scanf("%d", &pin) < 1000)
        {
        attempts++;
        printf("Please re-enter pin number: \n");
        if (attempts > 3)
        printf("Sorry you can't continue, contact your bank for assistance.");
        }
     else
     return attempts;
}//end getPin

[sl4nted]

hint: scanf doesn't return the number that it scanned

[imfrrreal]

I don't follow, sl4nted

[Dave_Sinkula]

And you need to loop with a loop of some sort. And you need to initialize uninitialized values before modifying/examining them.

[vart]

I don't follow, sl4nted

you should read the decription of the scanf and make a special point on the return value of that function to use it properly

[imfrrreal]

OMG I forgot to loop.

Duhh

Thank you!!!!

I'll try fixing that and if I have another issue I'll post.

[sl4nted]

if (scanf("%d", &pin) < 1000)

I assume your test to see if its less than 3 digits here.

try this

add another variable int ret; it will hold scanfs return
so
ret = scanf("%d", &pin);
printf("Returned: %d\n", ret);

should show you whats going wrong

[imfrrreal]

Ok, check out int getPin now.. It's still not working properly.. after 2 attempts it moves on to getReciept in main.

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

//Global Dec's
int getPin ();
void getReciept (void);
void menuChoose (void);

int main (void)
{
    //Local Dec's
    int attempts;
  
        
    printf("Welcome to Virtual Bank at West\n");
    attempts = getPin ();
    if (attempts < 3)
    {
    getReciept();
    menuChoose();
}
    else
    system("pause");
    return 0;
}
    
//getPin

int getPin ()
{
    int pin;
    int attempts = 0;
    printf("Please enter pin number: \n");
    scanf("%d", &pin);
     while (pin < 1000)
        {
        attempts++;
          
        if (attempts < 3)
        {
        printf("Please re-enter your pin: \n");
        scanf("%d", &pin);
        } 
        else
        {
        printf("Sorry you can't continue, contact your bank for assistance.");
        return attempts;
         }
        system("pause");
        return attempts;
        }
}//end getPin

[vart]

you problem is indentation - fix it and you will see the problem with the getPin function (when and what it returns...
For example what it will return when 1001 is entered

[imfrrreal]

nevermind

[whiteflags]

I prefer to do error checking with a string myself. That way, input errors are independent of and easier to find than problems with scanf or magic numbers.

Here's something that would work. I doubt it's bulletproof, and it should help you nonetheless:

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

int getPin ( int *somepin )
{
   char pinstr[6]; /* Just big enough I think */
   if ( fgets(pinstr, sizeof pinstr, stdin) != NULL )
   {
      char *tail = pinstr;
      while ( isdigit(*tail) )
      {
         tail++;
      }

      if ( tail - pinstr == 4 /* checking length */ && (*tail == '\0' || *tail == '\n') )
      {
         *somepin = atoi(pinstr);
         return 1; /* success!! */
      }
   }

   return 0; /* failure :( */
}

int main ( void )
{
   int mypin, attempts = 0;
   while ( attempts < 3 )
   {
      printf("Enter PIN: ");
      fflush(stdout);
      if ( getPin(&mypin) )
      {
         attempts++;
      }
      else
      {
         printf("Not a valid entry.\n");
      }
   }

   return 0;
}

/* output:
Enter PIN: q123
Not a valid entry.
Enter PIN:   12
Not a valid entry.
Enter PIN: aswd
Not a valid entry.
Enter PIN: 1234
Enter PIN: 1234
Enter PIN: 1001
*/

It doesn't have to be difficult.