Technical Stuff

#include<stdio.h>
#define STACKSIZE 20
//stack size is 20
int stack[STACKSIZE]={0};
//top of the stack initially -1 which means empty
int tos=-1;
void push(int ele)
{
 if(tos>=STACKSIZE)
 {
 printf("err: Stack is full\n");
 }
 else
 {
 tos++;
 stack[tos] = ele; 
 }
}
int pop()
{
 if(tos==-1)
 {
 printf("err: stack is empty\n");
 }
 else
 {
 int temp = stack[tos];
 tos--;
 printf("poped element from the stack is %d\n",temp);
 return temp; 
 }
}
void display()
{
 int i;
 for(i=0;i<=tos;i++)
 printf(" %d\n",stack[i]);
 if(tos== -1)
 {
 printf("err: stack is empty\n");
 return;
 }
}
int main()
{
 int ch,ele;
 printf("enter the choice 1-push 2-pop 3-display 9-exit\n");
 scanf("%d",&ch);
 while(ch!=9)
 {
 switch(ch)
 {
 case 1: printf("Enter the ele to push\n");
 scanf("%d",&ele);
 push(ele);
 break;
 case 2: ele = pop();
 break;
 case 3: display();
 break;
 case 4:
 break;
 default:
 break;
 }
 printf("enter the choice 1-push 2-pop 3-display 9-exit\n");
 scanf("%d",&ch);
 }
}