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Pointers and Arrays revisited

#include <stdio.h>
int main(void) {
 int* ptr;
 int my_array[] = {11,22,33,44};
 ptr = &my_array[0];
 for (i=0;i<4;i++) {
  printf("my_array[%d] = %d   ", i, my_array[i]);
  printf("ptr + %d  = %d\n", i, (*ptr+1));
 }
 return 0;
}

my_array[0] = 11  ptr + 0 = 11;
my_array[1] = 22  ptr + 4 = 22;
my_array[2] = 33  ptr + 8 = 33;
my_array[3] = 44  ptr + 12 = 44;

This shows the following facts about pointers and arrays:

  1. The address of an array at element 0 (&my_array[0]) is the same as the array name.

  2. The following statements are therefore equivalent: ptr = &my_array[0]; and ptr = my_array;.

  3. An array is a pointer to the first element of the array.

  4. But an array cannot be re-assigned like a pointer. While my_array == ptr the following code does not work:

    int my_array[5];
int* prt;
ptr = my_array;
my_array = ptr; // ERROR: an array is NOT an lvalue