Pointers

When an Array is a Pointer
• When an array is defined the required space is allocated to store the whole array, whereas, when a pointer is defined space is allocated for single pointer variable
• To the compiler an array is an address, whereas, a pointer is the address of an address
• Array names are similar to constant pointers. They point to a constant location
• As a consequence of the above, array names cannot be rewritten as pointers
• When arrays are used as function arguments, they are converted to pointers by the compiler
• A subscript is equivalent to an offset from a (base) pointer
  int_array[10] refers to an address which is offset by 10*sizeof(int) from the address of the beginning of the array (base address)
• The compiler automatically scales a subscript to the size of the object pointed at
• Consider the following declaration:
  int int_array[10], *p, i=2;
  The following are equivalent ways of accessing int_array[i]:
  

  p = int_array; p[i];

  p = int_array; *(p + i);

  p = int_array + i; *p;



• The following are equivalent ways of processing an array:
  

   for (int i = 0; i < 10; i++)
  	int_array[i] = 0; // Using array-subscript notation 
  
  
  int* p;
  p = int_array;
  for  (int i = 0; i < 10; i++)
  	p[i] = 0; // Using pointer-subscript notation
  
  
  int* p;
  p = int_array;
  for (int i = 0; i < 10; i++)
  	*(p + i) = 0; // Using pointer + offset notation
  		      // - identical to previous example
  
  
  int* p;
  p = int_array;
  for (int i = 0; i < 10; i++)
  	*p++ = 0; // Using pointer dereferencing notation
  		  // and manipulating the pointer variable