Pointers – Difference between Array and Pointer

by 
int a[]={5,6,7,8};
int *p= a;

Note that in case of arrays(In most cases), say array a, the ADDRESS_OF a is same as ADDRESS_OF first element of the array.ie, ADDRESS_OF(a) is same as ADDRESS_OF(a[0]). & is the ADDRESS_OF operator and hence in case of an array a, &a and &a[0] are all the same.

I have already emphasized that in most cases, the name of an array is converted into the address of its first element; one notable exception being when it is the operand of sizeof, which is essential if the stuff to do with malloc is to work. Another case is when an array name is the operand of the & address-of operator. Here, it is converted into the address of the whole array. What’s the difference? Even if you think that addresses would be in some way ‘the same’, the critical difference is that they have different types. For an array of n elements of type T, then the address of the first element has type ‘pointer to T’; the address of the whole array has type ‘pointer to array of n elements of type T’; clearly very different.

Here’s an example of it:

int ar[10];
int *ip;
int (*ar10i)[10];       /* pointer to array of 10 ints */

ip = ar;                /* address of first element */


ip = &ar[0];            /* address of first element */
ar10i = &ar;            /* address of whole array */

For more information you can refer The C Book.

More Related Contents:

  1. What is the output of the following code in C? [closed]
  2. Incorrect result in c code
  3. whats the difference between dynamic memory allocation and normal memory allocation?
  4. pointer to string concept in c [closed]
  5. Pointer manipulation inside function
  6. Changing address contained by pointer using function
  7. Why is the asterisk before the variable name, rather than after the type?
  8. What’s the difference between a VLA and dynamic memory allocation via malloc?
  9. Why does this implementation of offsetof() work?
  10. Why can’t I cast a function pointer to (void *)?
  11. Constant pointer vs Pointer to constant [duplicate]
  12. Can the size of pointers vary between data and function pointers?
  13. Function to dynamically allocate matrix
  14. Using fseek with a file pointer that points to stdin
  15. What happens in OS when we dereference a NULL pointer in C?
  16. Pointer vs array in C, non-trivial difference
  17. Are “malloc(sizeof(struct a *))” and “malloc(sizeof(struct a))” the same?
  18. C – SizeOf Pointers
  19. Swapping pointers in C (char, int)
  20. What is double star (eg. NSError **)?
  21. Where in memory are string literals ? stack / heap? [duplicate]
  22. How to include a dynamic array INSIDE a struct in C?
  23. C difference between *[] and **
  24. Difference between *ptr[10] and (*ptr)[10]
  25. How are we able to access the pointer after deallocating the memory?
  26. When is it valid to access a pointer to a “dead” object?
  27. How to check if a pointer is freed already in C?
  28. Returning a struct pointer
  29. Casting void pointers
  30. Cast T[][] to T*

Leave a Comment