Loops practise(ASCII CODE RETURN at EVERY INDEX)

#include<iostream>
using namespace std;
#include<conio.h>
void main()
{
char a[20];
int i=0;
char *p;
for(i=0;i<=20;i++)
{
a[i]==NULL;
}
cout<<"enter name ";
cin>>a;
for(i=0;i<20 ;i++)
{
p=&a[i];
if(*p!=0)
cout<<"ASCII code at array indexes "<<i<<" "<<int(*p)<<" \n";
else
break;
}

_getch();
}