What's the meaning of "int * * k"?

Question

I am beginner of C Programming language. I saw a code on the book:

#include<stdio.h>
int main(){
    int * * k, *a, b=100;

    a = &b;
    k = &a;
    printf("%d\n",* * k);
}

I don't know the meaning of int * *k. Is that a integer pointer or value? what will it point to? what will it contains/store? what's the use of this variable? How can I understand this expression?

It's two level pointer dereferencing. – haccks Feb 14 '17 at 06:32 — haccks, Feb 14 '17 at 06:32
"k" is a pointer that point to an integer pointer – zzn Feb 14 '17 at 06:33 — zzn, Feb 14 '17 at 06:33

msc · Answer 1 · 2017-04-20T05:16:56.947

8

int **k

k is a pointer to pointer to int(double pointer) and holds an address of some other pointer variable.

In your example:

 int  b = 100;   /* 'b' is an int, initialized to value 100 */
 int *a = &b;  /* a is a pointer-to-int*/
 int **k = &a; /* k is a pointer-to-pointer-to-int */

See below picture for better understanding:

edited Apr 20 '17 at 05:16

answered Feb 14 '17 at 06:34

msc

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Thank you. can you tell me in what situation this pointer-to-a-pointer will be used? – Bing Sun Feb 14 '17 at 07:31
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@BingSun When we want a list of words (a sentence), We can use that. – msc Feb 14 '17 at 07:33
1

@BingSun See stack overflow question : http://stackoverflow.com/questions/5580761/why-use-double-pointer-or-why-use-pointers-to-pointers – msc Feb 14 '17 at 07:34
1

I think I got it now. Thank you! – Bing Sun Feb 14 '17 at 07:37

Tony Tannous · Answer 2 · 2017-02-14T07:44:48.317

2

int** k is a pointer to an int pointer.

It stores a memory address, in that memory address there another memory address in which some integer value is stored.

edited Feb 14 '17 at 07:44

answered Feb 14 '17 at 06:32

Tony Tannous

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score 1 · Answer 3 · answered Feb 14 '17 at 06:35

1

It's called double pointer. It can be used to store address from single pointer.

You can also create triple pointer to store address from double pointer.

Example: int ***k;

answered Feb 14 '17 at 06:35

algojava

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score 1 · Answer 4 · answered Feb 14 '17 at 06:38

1

This is called pointer to a pointer.

Here, the output for **k is 100, the value of b.

  *(*k) = *(a) = *(address of b) = value of b

answered Feb 14 '17 at 06:38

Pooja N

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score 1 · Answer 5 · answered Feb 14 '17 at 06:39

*k

means some code will get a value from address k later.

*(*k)

means some code will get a value from address (*k) later.

int **k

means k is intended to be used for address dereferencing for integer use but with a second level. Having this * character just behind a variable name at its definition, makes it a pointer. So k is a pointer to a pointer to an integer.

To get the value of cell that a pointer points to,

*k

is used just like in the definition. Then when it is a second-order pointer then

**k

is used to get its pointed value.

What's the meaning of "int * * k"?

5 Answers5