What is the data type of pointer variables?

Question

I refereed the following link,

Link1 Link 2

In the above link1 it was mentioned in answer that \"Pointers are of pointer type\".

I jus

Answer 1

You've asked two different questions.

Your title asks "What is the data type of pointer variables?". The answer is simple: a pointer variable is of some pointer type. For example, given:

int *ptr;

ptr is a pointer object, and its type is int*, which is a pointer type.

The body of your question asks whether "a pointer is a data type or not". By any reasonable definition of the phrase "data type", pointer types are data types.

The C standard never defines the phrase "data type", but it does use it (informally) in several places. It happens that none of the uses of the phrase "data type" in the standard refer to pointer types, but that doesn't tell us anything.

The standard says that all types are either function types or object types. Object types are further divided into a number of categories: integer types, array types, structure types, union types, pointer types, etc. A pointer type can be a pointer to an object type or a pointer to a function type. (It can be a pointer to an incomplete object type; as of the 2011 standard, incomplete types are classified as object types.)

Another ambiguity in your question is your use of the word "pointer". The word "pointer" by itself commonly refers to an object of pointer type, but it can also refer to a value of pointer type (for example, the standard says that malloc returns a pointer). It's better to use "pointer" as an adjective rather than as a noun, so you can have:

• a pointer type;
• a pointer object (an object of pointer type);
• a pointer expression (an expression that yields a result of pointer type); or
• a pointer value (the value, of pointer type, yielded by a pointer expression).

A pointer type is an object type. A pointer object is an object; an object is defined by the standard as a "region of data storage in the execution environment, the contents of which can represent values". So a pointer object is a region of data storage.

Following your Link 2, some random person on the Internet wrote that "Pointers are simply a variable that hold an address so one could argue that a pointer is a data type, but it is not defined as a data type (per "The C Programming Language". Kernighan & Ritchie)". I don't know whether K&R defines the term "data type"; since this person didn't provide a specific citation, it's difficult to tell without searching the book. But it's the standard, not K&R, that defines the language.

I'm curious: why would you think that a pointer type wouldn't be considered a data type?