Program implements array as a stack.

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

#define MAX 10

struct stack
{
int arr[MAX] ;
int top ;
} ;

void initstack ( struct stack * ) ;
void push ( struct stack *, int item ) ;
int pop ( struct stack * ) ;

void main( )
{
struct stack s ;
int i ;

clrscr( ) ;

initstack ( &s ) ;

push ( &s, 11 ) ;
push ( &s, 23 ) ;
push ( &s, -8 ) ;
push ( &s, 16 ) ;
push ( &s, 27 ) ;
push ( &s, 14 ) ;
push ( &s, 20 ) ;
push ( &s, 39 ) ;
push ( &s, 2 ) ;
push ( &s, 15 ) ;
push ( &s, 7 ) ;

i = pop ( &s ) ;
printf ( "\n\nItem popped: %d", i ) ;

i = pop ( &s ) ;
printf ( "\nItem popped: %d", i ) ;

i = pop ( &s ) ;
printf ( "\nItem popped: %d", i ) ;

i = pop ( &s ) ;
printf ( "\nItem popped: %d", i ) ;

i = pop ( &s ) ;
printf ( "\nItem popped: %d", i ) ;

getch( ) ;
}

/* intializes the stack */
void initstack ( struct stack *s )
{
s -> top = -1 ;
}

/* adds an element to the stack */
void push ( struct stack *s, int item )
{
if ( s -> top == MAX - 1 )
{
printf ( "\nStack is full." ) ;
return ;
}
s -> top++ ;
s -> arr[s ->top] = item ;
}

/* removes an element from the stack */
int pop ( struct stack *s )
{
int data ;
if ( s -> top == -1 )
{
printf ( "\nStack is empty." ) ;
return NULL ;
}
data = s -> arr[s -> top] ;
s -> top-- ;
return data ;
}