Stack Program in C (Introduction)

// C Program for Implmentation of stack (array) using structure
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>

// A structure to represent a stack 
struct Stack
{
  int top;
  int maxSize;
  int *array;
};

struct Stack *create (int max)
{
  struct Stack *stack = (struct Stack *) malloc (sizeof (struct Stack));
  stack->maxSize = max;
  stack->top = -1;
  stack->array = (int *) malloc (stack->maxSize * sizeof (int));
  //here above memory for array is being created
  // size would be 10*4 = 40
  return stack;
}

// Checking with this function is stack is full or not
// Will return true is stack is full else false 
//Stack is full when top is equal to the last index 
int isFull (struct Stack *stack)
{
  if (stack->top == stack->maxSize - 1)
    {
      printf ("Will not be able to push maxSize reached\n");
    }
  // Since array starts from 0, and maxSize starts from 1
  return stack->top == stack->maxSize - 1;
}

// By definition the Stack is empty when top is equal to -1 
// Will return true if top is -1
int isEmpty (struct Stack *stack)
{
  return stack->top == -1;
}

// Push function here, inserts value in stack and increments stack top by 1
void push (struct Stack *stack, int item)
{
  if (isFull (stack))
    return;
  stack->array[++stack->top] = item;
  printf ("We have pushed %d to stack\n", item);
}

// Function to remove an item from stack.  It decreases top by 1 
int pop (struct Stack *stack)
{
  if (isEmpty (stack))
    return INT_MIN;
  return stack->array[stack->top--];
}

// Function to return the top from stack without removing it 
int peek (struct Stack *stack)
{
  if (isEmpty (stack))
    return INT_MIN;
  return stack->array[stack->top];
}

int main ()
{
  struct Stack *stack = create (10);

  push (stack, 5);
  push (stack, 10);
  push (stack, 15);

  int flag = 1;
  while (flag)
    {
      if (!isEmpty (stack))
	printf ("We have popped %d from stack\n", pop (stack));
      else
	printf ("Can't Pop stack must be empty\n");
      flag = 0;
    }
  return 0;
}