Stacks

That is a stack program - I tried to change from integers to characters so when you enter a single char of a-z. I ran the program then it displayed shown below:

Enter a number: to stop: a
Enter a number: to stop: Enter a number: to stop: b
Enter a number: to stop: Enter a number: to stop: c
Enter a number: to stop: Enter a number: to stop: d
Enter a number: to stop: Enter a number: to stop: e
Enter a number: to stop: Enter a number: to stop: ^Z


The list of numbers reversed:

Code:

  e


  d


  c


  b


  a
Press any key to continue . . .


Why did it appear the output twice "Enter a number:  to stop: Enter a number:  to stop:"?

The code is below:


 #include 
#include 
#include "stacksADT.h"

int main (void)
{
        int  done = false;
        char* dataPtr;

        STACK* stack;

        stack = createStack ();

        while (!done)
           {
            dataPtr = (char*) malloc (sizeof(char));
            printf ("Enter a number:  to stop: ");
            if ((scanf ("%c" , dataPtr)) == EOF 
                   || fullStack (stack))
               done = true;
            else
               pushStack (stack, dataPtr);
           }

        printf ("\n\nThe list of numbers reversed:\n");
        while (!emptyStack (stack))
           {
            dataPtr = (char*)popStack (stack);
            printf ("%3c\n", *dataPtr);
            free (dataPtr);
           }

        destroyStack (stack);
        system("pause");
        return 0;
}