Write a C program to implement stack. Stack is a LIFO data strcuture
 * LIFO - Last in First Out                                                
 * Perform PUSH(insert operation), POP(Delete operation) and Display stack 
#include <stdio.h>
#include <conio.h>
#define MAXSIZE 5
struct stack /* Structure definition for stack */
{
int stk[MAXSIZE];
int top;
};
typedef struct stack STACK;
STACK s;
/* Function declaration/Prototype*/

void push (void);
int pop(void);
void display (void);

void main ()
{
int choice;
int option = 1;

clrscr ();

s.top = -1;

printf ("STACK OPERATIONn");
while (option)
{
printf ("------------------------------------------n");
printf (" 1 --> PUSH n");
printf (" 2 --> POP n");
printf (" 3 --> DISPLAY n");
printf (" 4 --> EXIT n");
printf ("------------------------------------------n");

printf ("Enter your choicen");
scanf ("%d", &choice);

switch (choice)
{
case 1: push();
break;
case 2: pop();
break;
case 3: display();
break;
case 4: return;
}

fflush (stdin);
printf ("Do you want to continue(Type 0 or 1)?n");
scanf ("%d", &option);
}
}

/*Function to add an element to the stack*/
void push ()
{
int num;
if (s.top == (MAXSIZE - 1))
{
printf ("Stack is Fulln");
return;
}
else
{
printf ("Enter the element to be pushedn");
scanf ("%d", &num);
s.top = s.top + 1;
s.stk[s.top] = num;
}
return;
}


/*Function to delete an element from the stack*/
int pop ()
{
int num;
if (s.top == - 1)
{
printf ("Stack is Emptyn");
return (s.top);
}
else
{
num = s.stk[s.top];
printf ("poped element is = %dn", s.stk[s.top]);
s.top = s.top - 1;
}
return(num);
}

/*Function to display the status of the stack*/
void display ()
{
int i;
if (s.top == -1)
{
printf ("Stack is emptyn");
return;
}
else
{
printf ("nThe status of the stack isn");
for (i = s.top; i >= 0; i--)
{
printf ("%dn", s.stk[i]);
}
}
printf ("n");
}

/*---------------------------------------------------------------------------
Output
STACK OPERATION
------------------------------------------
1 --> PUSH
2 --> POP
3 --> DISPLAY
4 --> EXIT
------------------------------------------
Enter your choice
1
Enter the element to be pushed
23
Do you want to continue(Type 0 or 1)?
1
------------------------------------------
1 --> PUSH
2 --> POP
3 --> DISPLAY
4 --> EXIT
------------------------------------------
Enter your choice
1
Enter the element to be pushed
45
Do you want to continue(Type 0 or 1)?
1
------------------------------------------
1 --> PUSH
2 --> POP
3 --> DISPLAY
4 --> EXIT
------------------------------------------
Enter your choice
1
Enter the element to be pushed
78
Do you want to continue(Type 0 or 1)?
1
------------------------------------------
1 --> PUSH
2 --> POP
3 --> DISPLAY
4 --> EXIT
------------------------------------------
Enter your choice
3

The status of the stack is
78
45
23

Do you want to continue(Type 0 or 1)?
1
------------------------------------------
1 --> PUSH
2 --> POP
3 --> DISPLAY
4 --> EXIT
------------------------------------------
Enter your choice
2
poped element is = 78
Do you want to continue(Type 0 or 1)?
1
------------------------------------------
1 --> PUSH
2 --> POP
3 --> DISPLAY
4 --> EXIT
------------------------------------------
Enter your choice
3

The status of the stack is
45
23

Do you want to continue(Type 0 or 1)?
0
-----------------------------------------------------------------------------*/