What is the difference between p and a?

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Is array name a pointer in C?

What is the difference between p and a in C?

float a[10],*p; p=a;

`a` is an array of ten floats. `p` is a pointer to its first element. You can find this in any C textbook. — Fred Foo, Feb 03 '13 at 22:54
The relationship between arrays and pointers in C can be confusing. Section 6 of the [comp.lang.c FAQ](http://www.c-faq.com/) does an excellent job of explaining it. — Keith Thompson, Feb 03 '13 at 22:59

score 2 · Answer 1 · answered Feb 03 '13 at 22:56

2

If we define "difference" as the result of subtraction, there answer is zero:

assert((p-a) == 0);

...until you assign some other pointer value to p (which you cannot do with a, because it doesn't name a pointer variable: it names an array which decays to pointer in appropriate contexts; there are other contexts, e.g. sizeof(p)!=sizeof(a)).

answered Feb 03 '13 at 22:56

Anton Kovalenko

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I vote for the funniest answer of the day! – Sylvain Defresne Feb 03 '13 at 22:57
if const pointer a stores the adress of the first element of the array and pointer p stores the adress of the pointer a, they both represent the first element of the array? – user2038136 Feb 03 '13 at 23:15

score 2 · Answer 2 · answered Feb 03 '13 at 23:00

float a[10],*p; p=a;

a is an array 10 of float.

p is a pointer to float. It points to the first element of a.

In C arrays are not pointers. Arrays and pointers are two different types. For example:

sizeof a;   // compute the size of an array
sizeof p;   // compute the size of a pointer

p = &a[1];  // this is valid, p points to the second element of a
a = &p[1];  // this is not valid, you cannot assign to an array

What is the difference between p and a?

2 Answers2