What operation we can't do with pointers?

Question

I know this questions sounds odd but can you please say some operations we can't do with pointers but with arrays and other?

Check this out: http://www.tutorialspoint.com/cprogramming/c_pointer_arithmetic.htm — Rizier123, Dec 04 '14 at 05:58
Array operations and pointer operations are aliases of each other, so I don't think this question makes sense... — keshlam, Dec 04 '14 at 05:59
@keshlam i too felt the same but this was my interview question in a top most company:( — Techky, Dec 04 '14 at 06:25
@ChumaAcc: I think Mohit has the kind of answer they were looking for. — keshlam, Dec 04 '14 at 14:20
@keshlam To make things clearer here, I did not ask the question ;) — Mohit Jain, Jan 23 '17 at 05:23

score 2 · Accepted Answer · answered Dec 04 '14 at 06:02

2

You can not use sizeof sensefully

int arr[6] = {0};
int *p = &arr[0];

sizeof arr / sizeof arr[0] gives 6
sizeof p / sizeof p[0] may give 0, 1, 2 etc (1 on my 32 bit system)

If array is member of a struct, assignation operator (=) will (deep) copy value. But for pointer, only pointer (shallow) is copied.

struct str
{
  char name[100];
  char *city;
}a, b;
...
a = b;
a.name[0] = '\0'; // b.name[0] does not change
a.city[0] = '\0'; // b.city[0] changed

answered Dec 04 '14 at 06:02

Mohit Jain

30,259
8
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Can you please give brief explanation about deep and shallow copy? or refer me some link? – Techky Dec 04 '14 at 06:45
[This post](http://stackoverflow.com/questions/184710/what-is-the-difference-between-a-deep-copy-and-a-shallow-copy) covers very good explanation of deep copy and shallow copy. – Mohit Jain Dec 04 '14 at 06:58
Quibble: You can get sizeof(), but only of the pointer itself, not of the array. But yes, this is probably what they're looking for. – keshlam Dec 04 '14 at 14:19
Actually, looking at it from that angle, realloc() and free() could be considered another difference... but that's misleading, because not all pointers can be safely free()d/realloc()ed either, only those at the start of the malloc()ed memory block. – keshlam Dec 04 '14 at 14:25

score 0 · Answer 2 · answered Dec 04 '14 at 06:04

0

Pointers are used for storing address of dynamically allocated arrays and for arrays which are passed as arguments to functions. In other contexts, arrays and pointer are two different things,

for more you can take a look of this url http://www.geeksforgeeks.org/difference-pointer-array-c/

answered Dec 04 '14 at 06:04

Kandy

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9
21

I don't quite agree with the conclusion there. The *only* differences I can think of between array names and (valid) pointers are whether the space is allocated from heap or stack , and what sizeof() reports for them. They're more similar than different. – keshlam Dec 04 '14 at 14:26

What operation we can't do with pointers?

2 Answers2