C Pointers

Question 1

What is a pointer?

Answer 1

A pointer is a data type that contains a memory location

We can use a pointer to indirectly get to the values of variables.

Question 2

When we say pointers have two values, what values are we referring to?

Answer 2

The address to stored by the pointer

The value at the address where the pointer points

Question 3

What is the ‘&’ pointer operator?

Answer 3

Used to give the memory address of a variable

Question 4

What is the ‘*’ pointer operator?

Answer 4

Used to tell us to look through the pointer to the underlying data

Question 5

Does a pointer declaration creates space for the data?

Answer 5

NO!!!

Question 6

What is ‘pass by reference’

Answer 6

Declare a function parameter to be a pointer to the variable in the calling function.

foo( int *a ) {
a = 10; / Sets the variable in the caller to 10 */
}

main() {
int b;
foo( &b ); /* b returns with the value 10 */ }

Question 7

Basic Pointers

Answer 7

Declaration
int *p;
void *q;

Dereferencing
int *p;
*p = 7;

Assigning to a pointer from a regular variable int *p;
int a;
p = &a;

A value of NULL (from stdlib.h) is used for a non-existent memory address