C++ Arrays & pointers

C++ Arrays & pointers

can anyone help me with the following inequalities for arrays:
#include <stdio.h>
#define PRD(a) printf("%d", (a))
#define NL printf("\n");
int a[] = {0,1,2,3,4};
int main ()
{
int i;
int*p;
for (i=0; i<=4; i++) PRD(a[i]);
NL;
for (p=&a[0]; p<=&a[4]; p++) PRD(*p);
NL;
for (p=&a[0]; i=0; p+i<=a+4; i++) PRD(p[i]);
NL;
for (p=a, i=0; p+i<=a+4; p++, i++) PRD(*(p+i));
NL;
basically i dont understand the 4 loops, please kindly help to explain to me!