difference between pointer and address reference

Question

I'm not sure how to call this two pointer differently so please correct my terms.

#include <stdio.h>

int main()
{
    int arr[3]={10,20,30};
    int * ptr = &arr[0];// arr

    return 0;
}

is there some differences between arr and *ptr? Both pointed at the same address, but what's the difference.

There's are 1000s of question on this site. Please do some search. — P0W, Nov 17 '16 at 07:33
@ckruczek, no arrays and pointers are quite different until used in contexts where one decays to the other. — StoryTeller - Unslander Monica, Nov 17 '16 at 07:39
array type decays to pointer to the first element in certain cases, just FYI. — Sourav Ghosh, Nov 17 '16 at 07:42
[Is an array name a pointer in C?](http://stackoverflow.com/questions/1641957/is-an-array-name-a-pointer-in-c) — Lundin, Nov 17 '16 at 08:19

Gopi · Answer 1 · 2016-11-17T07:58:32.570

1

arr is an array and ptr is a pointer of type int.

There are differences . Let me list few

sizeof(arr) is different from sizeof(ptr)
You can do ptr++ pointer operation using ptr whereas arr++ is an invalid operation.

Going by your comment of what is the difference between pointer and array I have answered your question

int a = 10;
int b[5] = {1,2,3,45};
int *p = &a;
b = &a;  /* not valid */

b is a array and not a pointer so it can't hold address of a variable.

p = b;
p = p +1;

printf("%d\n",*p); /* valid as p is pointing to second element in the array */

b = b+1;

is not valid because array can't be a modifiable lvalue

edited Nov 17 '16 at 07:58

answered Nov 17 '16 at 07:36

Gopi

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Why was this downvoted? It's not the most complete answer that could be given, but it gives no mis-information. It may be worth nothing to the OP that *ptr is different from ptr. (*ptr = arr[0] = 10 whereas ptr = arr = &arr[0]) – Forrest Nov 17 '16 at 07:50
*(arr+1) is working also as *(ptr +1) – kingyum Nov 17 '16 at 07:54
@kingyum *(arr +1) = arr[1] . What you have to note is *(a+i) = a[i] – Gopi Nov 17 '16 at 07:55
why arr++ is not working? – kingyum Nov 17 '16 at 07:56
arr++ is not same as *(arr + 1) – Gopi Nov 17 '16 at 07:56
can you explain more about why arr++ is not valid? – kingyum Nov 17 '16 at 07:58
@kingyum Does my update help? – Gopi Nov 17 '16 at 08:00
yes, so the type is difference. and also is there any difference between arr[0] and *ptr other then the type? arr[0] is now allows arr[0]++ – kingyum Nov 17 '16 at 08:04
Gopi, this is personal question but what is your secret to study programming? and How long you been working with this kind of stuff? and I want to be a better programmer with lot of knowledge. reveal your secret – kingyum Nov 17 '16 at 08:15
@kingyum Keep learning. I amalso learning. There is no such secret – Gopi Nov 17 '16 at 08:18
@Gopi thanks for your help take care – kingyum Nov 17 '16 at 08:43

score -1 · Answer 2 · answered Nov 17 '16 at 07:38

-1

'is there some differences between arr and *ptr'

Yes, there is. For example sizeof(*ptr) is a size of int value, that is sizeof(int), while sizeof(arr) is a size of the whole array and equals 3*sizeof(int).

answered Nov 17 '16 at 07:38

CiaPan

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difference between pointer and address reference

2 Answers2