What is the significance of * in * ?

Question

My teacher mentioned (actually he just wrote it on the board and said nothing about it) this particular pointer but I don't understand the significance of it. The example he wrote on the board was this:

Book * book;

What does the pointer do when it is used like this?

@AndreyChernukha ... but I can't find a fitting close reason. — Mark Garcia, Jan 22 '14 at 06:30
My teacher is for some reason has issues understanding his students' questions. — grim_v3.0, Jan 22 '14 at 06:31
@JerryCoffin It's not a duplicate, asker doesn't know the significance of * operator, he is not asking about it's usage with `const` — Pratik Singhal, Jan 22 '14 at 06:33
@ps06756: Though that question *also* includes `const`, it (and the answers to it) also talk about the (in)significance of white space. — Jerry Coffin, Jan 22 '14 at 06:35
@Spook: See his comment to Paul Draper's answer, which makes it clear that whitespace is *exactly* what he doesn't (or didn't) understand. — Jerry Coffin, Jan 22 '14 at 06:40
Ok, I was judging basing on his question, not comments to answers. I guess, that a duplicate will be a good close reason after all. — Spook, Jan 22 '14 at 06:41
Okay, I just have to ask, why does the duplicate link point to a question that is marked as yet *another* [duplicate](http://stackoverflow.com/questions/2660633)? And then why is that marked as a duplicate of [two](http://stackoverflow.com/questions/558474) [more](http://stackoverflow.com/questions/377164)? The first of which, by the way, is marked a duplicate of [another](http://stackoverflow.com/questions/398395)! Why not point to the original, rather than an entire chain of duplicate questions? — Paul Draper, Jan 22 '14 at 06:50

score 1 · Accepted Answer · answered Jan 22 '14 at 06:23

1

The * is part of the type.

book is of type Book *, that is a pointer to a Book.

class Book {
};

Book * book1 = new Book();
Book * book2 = book1;
//now book1 and book2 point to the same Book

answered Jan 22 '14 at 06:23

Paul Draper

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I thought that Book *book is a pointer to a book, is Book * book just the same thing? – grim_v3.0 Jan 22 '14 at 06:24
@grim_v3.0 whitespaces do not matter here. – Samuel Jan 22 '14 at 06:25
@grim_v3.0, yes. `Book*book`, `Book *book`, `Book* book`, and `Book * book` are the same. – Paul Draper Jan 22 '14 at 06:26
So the only time a pointer has a noticable difference is with something like char* const or char const*? – grim_v3.0 Jan 22 '14 at 06:29

score 0 · Answer 2 · answered Jan 22 '14 at 06:29

Basically, using * can be used to define a pointer.
What your teacher meant was to declare a pointer to a object of type Book

    Book* book1  ; // Declare a pointer to a object of type Book
    Book bookObj ; 
    book1 = &bookObj ; // now book1 points to bookObj.

You can use * with any type(predefined as well as custome defined types in c++).
You can also use * to dereference a pointer.

   int num1 = 0 ; 
   int* num1p = &num1 ;  // pointer pointing to num1
   *num1p = 10 ;  // same as num1 = 10.

Hope this helps!

What is the significance of * in * ?

2 Answers2