How to write Simple Stack Program in C

#include<conio.h>
#include<stdio.h>
 

void PUSH();
void PEEP();
int POP();

int top=-1,item,a[10];

void main()
{

int i;
clrscr();

for(i=0;i<12;i++)
{

printf("\nEnter No: ");
scanf("%d",&item);

PUSH(item);

}

POP();

POP();

PEEP();

getch();

}

void PUSH(int itemx)
{

if(top>=10)
{

printf("\n\nStack is Overflow");

}
else
{

top=top+1;
a[top]=itemx;

}

}
void PEEP()
{

int itemx=a[top];

printf("\n\nTop value : %d",itemx);

}
int POP()
{

if(top<=0)
{

printf("\nStack is Underflow ");

}
else
{

item=a[top];
a[top]=NULL;
top=top-1;

printf("\n\tElement POPED ");

return item;

}

}