C Program to implement Stacks

/* Implement Stacks */

#include<stdio.h>
#include<conio.h>

typedef struct stack
{
int data[20];
int top;
}stack;

void init(stack *);
int empty(stack *);
int full(stack *);
int pop(stack *);
void push(stack *,int);
void print(stack *);

void main()
{
stack s;
int x, op;
init(&s);
clrscr();
do
 {
  printf("\n\n1)Push\n2)Pop\n3)Print\n4)Quit");
  printf("\nEnter your choice");
  scanf("%d",&op);
  switch(op)
  {
  case 1 : printf("Enter a number");
  scanf("%d",&x);
  if(!full(&s))
  push(&s,x);
  else
  printf("Stack is full");
  break;
  case 2 : if(!empty(&s))
  {
  x=pop(&s);
  printf("Popped value=%d",x);
  }
  else
  printf("Stack is empty");
  break;
  case 3 :
  if(empty(&s))
  printf("Stack is empty");
  else
   print(&s);
  break;
  }
 }while(op!=4);
}

void init(stack *s)
{
 s->top=-1 ;
}

int empty(stack *s)
{
 if(s->top==-1)
  return(1);
 return(0);
}

int full(stack *s)
{
 if(s->top==19)
  return(1);
 return(0);
}

void push(stack *s,int x)
{
 s->top=s->top+1;
 s->data[s->top]=x;
}

int pop(stack *s)
{
 int x;
 x=s->data[s->top];
 s->top=s->top-1;
 return(x);
}

void print(stack *s)
{
 int i;
 printf("\n");
 for(i=s->top;i>=0;i--)
  printf("%d",s->data[i]);
}