Click here to Skip to main content
11,925,022 members (51,681 online)
Rate this:
Please Sign up or sign in to vote.
See more: C++
int a[3][4]={1,2,3,4,5,6,7,8,9,10,11,12};
int (*ptr)[4]=a;
what do ptr and *ptr mean in this context? Why ptr and *ptr point to the same meory address
Posted 21-Apr-13 5:29am

1 solution

Rate this: bad
Please Sign up or sign in to vote.

Solution 1

ptr is a variable, in this case it is declared as a pointer to an array of 4 integers.

To read the declaration, start with the name of the variable (ptr in this case) and work out, going right when possible:
int (*ptr)[4]=a;
"ptr is..."
We can't go right because we need a matching bracket first, so we go left
int (*ptr)[4]=a;
"ptr is a pointer to..."
Now we have closed the brackets so we can go right again:
int (*ptr)[4]=a;
"ptr is a pointer to an array of four...
The equals ends teh declaration, so we have to go left again
int (*ptr)[4]=a;
int (*ptr)[4]=a;
"ptr is a pointer to an array of integers"
And the rest of teh line assigns a suitable value.

So when you use ptr later in your code, you are referring to the instance of an array of three arrays of four integers.
When you refer to *ptr in your code you are referring to one of the arrays of four integers, because the "*" dereferences the pointer.

Did that make sense?
CPallini 21-Apr-13 11:56am
Yes, it did.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

  Print Answers RSS
Top Experts
Last 24hrsThis month

Advertise | Privacy | Mobile
Web03 | 2.8.151125.3 | Last Updated 21 Apr 2013
Copyright © CodeProject, 1999-2015
All Rights Reserved. Terms of Service
Layout: fixed | fluid

CodeProject, 503-250 Ferrand Drive Toronto Ontario, M3C 3G8 Canada +1 416-849-8900 x 100