C Program Stack Operation

/*C Program Stack Operation*/
#include<stdio.h>
#include<conio.h>
#define SIZE 5
int top=-1,S[SIZE];
void push()
{
    int item;
    if(top==SIZE-1)
        printf("stack overflow \n");
    else
    {
        printf(" enter the element \n");
        scanf("%d",&item);
        top=top++;
        S[top]=item;
    }
}
void pop()
{
    int x;
    if(top==-1)
    {
        printf("stack is underflow!\n");
        return;
    }
    x=S[top];
    printf("poped element=%d \n",x);
    top--;
}
void display()
{
    int i;
    if(top==-1)
    {
        printf(" stack is underflow!\n");
        return;
    }
    printf(" stack contents are:\n");
    for(i=0; i<=top; i++)
    {
        printf("%d \n",S[i]);
    }
}
void main()
{
    int ch;

    for(;;)
    {
        printf("1.PUSH\t2.POP\t3.DISPLAY\t4.EXIT\n");
        printf("enter the choice: \n");
        scanf("%d",&ch);
        switch(ch)
        {
        case 1:
            push();
            break;
        case 2:
            pop();
            break;
        case 3:
            display();
            break;
        default:
            exit(0);
        }

    }
}

Out Put:

1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
1
 enter the element
1
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
1
 enter the element
2
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
1
 enter the element
3
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
1
 enter the element
4
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
1
 enter the element
5
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
1
stack overflow
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
3
 stack contents are:
1
2
3
4
5
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
2
poped element=5
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
2
poped element=4
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
2
poped element=3
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
2
poped element=2
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
2
poped element=1
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
2
stack is underflow!
1.PUSH  2.POP   3.DISPLAY       4.EXIT
enter the choice:
4