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#include <stdio.h>
 
struct node
{
       int info;
       struct node * next;
}*top,*temp;
 
 
void PUSH(int item)
{
struct node *newnode;
newnode = (struct node *) malloc ( sizeof(struct node) );
 
if(newnode==NULL)
printf(" NO SPACE LEFT ");
else
{
    
newnode->info=item;
 
if( top == NULL )
{ 
newnode->next=NULL;
top=newnode;
}
else 
{ 
newnode->next=top;
top=newnode;
}
 
} //end of outer else
}// end of func
 
 
void POP()
{
if(top==NULL)
printf("\n Stack Empty. \n");
else
{
printf("\n Node with Info=%d is deleted. \n", top->info);
temp=top;
top=top->next;
free(temp);
}
}
 
void DISPLAY()
{
if(top==NULL)
printf("\n Stack is empty. ");
else
{
temp=top;
 
printf("\n");
while(temp!=NULL)
{
printf("\n |%d| ", temp->info);
temp=temp->next;
}
printf("\n");
}//end of else
}     
 
 
int main()
{
    int item,ch=1;
    top=NULL;
 
    
   while(ch!=4)
    {
    printf("\n MENU: ");
    printf("\n 1. Insert a node. ");
    printf("\n 2. Delete a node. ");
    printf("\n 3. Display Stack. ");
    printf("\n 4. EXIT \n Your Choice: ");
    scanf("%d",&ch);
    
    switch(ch)
    {
    case 1: //INSERT
        
    printf("\n ENTER ITEM: ");
    scanf("%d", &item);
    
    PUSH(item);
    break;
    
    case 2: //DELETE
    POP();
    break;
    
    case 3: //DISPLAY
    DISPLAY();
    break;
    
    case 4: 
    printf("\n Exiting.. ");
    break;
    
    default: printf(" INVALID CHOICE. ");
    
    }
    
    }; //end of while loop
    return 0;
    
}