Question

see i have seen some code like

int (*b)[10];

which means

declare b as pointer to array 10 of int

so i want to ask you what is the purpose of doing this ?

why don’t we write instead of that just

int array[10];

and use as passing address of array.

both are same or any difference ?

Edit :
Dont be confuse with

int *b[10];  // this one declare b as array 10 of pointer to int

and

int (*b)[10];  // this one declare b as pointer to array 10 of int

one more Edit

see int (*b)[10];

1>will allocate memory for 10 elements of int and the address of that memory will be assigned to b ?

or

2>there will be no memory allocated for array. here it says b is capable of holding address of and int array of 10 element ?

which option is right ?
if any one is right then why one should use this complex syntax rather then using different method?

Answer 1

There’s a difference actually. In int b[10], b is a pointer constant (which means it can be used to modify its underlying data but it can’t be changed to point to something else). The pointer in int (*b)[10] on the other hand can be changed to point to something else (as well as being able to change its underlying data of course). So the difference is that by saying that b is int (*b)[10]; you’re hereby warning the next developer who sees your code that this b can point to something else somewhere in the code. That’s why – obviously – don’t do that except if you really intend to change what b is pointing to (otherwise you’re just confusing who’ll come after you).

Regarding your question, I checked using sizeof(b).

int (*b)[10] ==> sizeof(b) is 4 (which means no memory allocated – Option 2).

int b[10] ==> sizeof(b) is 40 (which means memory is allocated as expected – Option 1).

Look at this:

int (*b)[10];

int x[10];
b = &x;

This compiled. Change the size of the array to anything else. It’ll not compile! This means that you’re extremely correct :-D. Option 2 is written perfectly: This pointer can only point to an array of size 10 and nothing else.

[Added as per request of question owner]

What’s the advantage of such a syntax? It’s just a feature that’s already there, and maybe it’s useful for somebody. This is how I understand it (and please correct me if wrong): For example, you can say: string (*names_of_players_in_soccer_team)[11]; and the advantage is – obviously – restricting the array to be exactly 11 names to handle the application logic – the team must actually have exactly 11 names. This gives more readability for those who’ll read your code, and emphasizes its correctness…