pointers

[gretchen1]

I am having a hard time with this:

Which statement is true given the following declaration:

int n=5, *p=&n;

a) p is a pointer initialized to point to n.
b) p is a pointer initialized to the value 5.
c) n and p are both pointer variables.
d) The declaration contains a syntax error.

[beacon]

Think of a pointer as a variable that has to have an asterisk before it. That's the only difference between the two.

If n is an integer, it will hold an integer value.

If *p is declared as an integer, it will hold the address for an integer value, which means that when *p is dereferenced, you will get an integer returned.

However, even though n and *p are both integers, they have to be declared separately just like a float and a double would, or how a string and a character would.

Does this clear it up a little?

[drhowarddrfine]

Assuming *p is declared as a pointer to an integer:
int *p;
you are saying p points at an integer.

Saying *p=&n is saying make the integer p is pointing at equal to & (the address of) the integer n. But p is supposed to point to an integer so this is incorrect.

[Banfa]

Saying *p=&n is saying make the integer p is pointing at equal to & (the address of) the integer n. But p is supposed to point to an integer so this is incorrect.

Not in initialisation

[code=c]
int n=5;
int *p;

*p = &n;
[/code]In this example p is declared and then not initialised. This code says make the int p points at equal to the address of the integer n (probably but not always wrong).

[code=c]
int n=5;
int *p = &n;
[/code]In this code p is declared and initialised at the same time. This says p is a pointer to an integer and it's value is the address of the integer n.

These 2 code sames result in different assignments, the first assigns to *p and the second assigns to p.