1. Implementation of stack using array

/**********************************************************************************************************
TITLE: Implementation of Stack using Array.
**********************************************************************************************************/

#include<stdio.h>
#include<stdlib.h>
#define SIZE 10

//Structure declaration
typedef struct
{
	float a[SIZE]; //stack of floats
	int tos;
}Stack;

int isEmpty(Stack *p)
{
    if ((p->tos)== -1)//checks if stack is empty
        return (1);
    else
        return (0);
}

int isFull(Stack *p)
{
    if ((p->tos)==SIZE-1)//checks if stack is full
        return (1);
    else
        return (0);

}

//Push Function
void push (Stack *p, float x)
{
    if (isFull(p))//if stack is full
    {
        printf("Stack is overflown\n");
        exit(1);
    }
    else
    {
        p->tos++;//increment tos
        printf("The pushed element is %f\n",x);
        p->a[p->tos]=x;//adding element to the top of the stack
    }
}

//Pop Function
float pop(Stack *p)
{
    if (isEmpty(p))//if stack is full
    {
        printf("Stack is empty\n");
        exit(1);
    }
    else
    {
		return(p->a[p->tos--]);//removing element from the top of the stack
    }
}

//Peek function
float peek(Stack s)
{
    return s.a[s.tos]; //return top element of stack

}

//Display function
void display(Stack s)
{
    int i;
    for(i = s.tos; i>=0 ; i--)
    {
        printf("%f\t",s.a[i]);
    }
}

//No.of elements in the stack
int size(Stack *p)
{
   printf("%d",p->tos+1);//index of top of the stack + 1
}


//Main starts
int main()
{
Stack s1; //s1 is variable of type stack
float x,data;
int option;

s1.tos = -1; //top of stack initialized to -1
	do
	{
		printf("\nEnter the choice 1.Push 2.Pop 3.Peek 4.Display 5.No.of elements in the stack\n");
		scanf("%d",&option);

		switch(option)
		{
			case 1:
				printf("Enter the element to push\n");
				scanf("%f",&x);
				push(&s1,x);
				break;
			case 2:
				data = pop(&s1);
				printf("\nThe popped element is %f\n",data);
				break;
			case 3:
				printf("The top element is %f\n",peek(s1));
				break;
			case 4:
				printf("\nThe stack contents are :\n");
				display(s1);
				break;
			case 5:
				printf("\nNo. of elements in the stack:\n");
				size(&s1);
				break;
			case 6:
				exit(0); //exit from program with exit status 0

		}
	}while(1);//while always true
	return 0;
}