Program implements linked list as a stack.

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

/* structure containing data part and linkpart */
struct node
{
int data ;
struct node *link ;
} ;

void push ( struct node **, int ) ;
int pop ( struct node ** ) ;
void delstack ( struct node ** ) ;

void main( )
{
struct node *s = NULL ;
int i ;

clrscr( ) ;

push ( &s, 14 ) ;
push ( &s, -3 ) ;
push ( &s, 18 ) ;
push ( &s, 29 ) ;
push ( &s, 31 ) ;
push ( &s, 16 ) ;

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

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

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

delstack ( &s ) ;

getch( ) ;
}

/* adds a new node to the stack as linked list */
void push ( struct node **top, int item )
{
struct node *temp ;
temp = ( struct node * ) malloc ( sizeof ( struct node ) ) ;

if ( temp == NULL )
printf ( "\nStack is full." ) ;

temp -> data = item ;
temp -> link = *top ;
*top = temp ;
}

/* pops an element from the stack */
int pop ( struct node **top )
{
struct node *temp ;
int item ;

if ( *top == NULL )
{
printf ( "\nStack is empty." ) ;
return NULL ;
}

temp = *top ;
item = temp -> data ;
*top = ( *top ) -> link ;

free ( temp ) ;
return item ;
}

/* deallocates memory */
void delstack ( struct node **top )
{
struct node *temp ;

if ( *top == NULL )
return ;

while ( *top != NULL )
{
temp = *top ;
*top = ( *top ) -> link ;
free ( temp ) ;
}
}