C Pointers: What are they and how do you use them?

What is a pointer?

• If you have a variable ‘var’ in your program, ‘&var’ will give you the address in memory of the variable ‘var’.
• Pointer variables are special variables that are used to store addresses rather than values.
• A pointer is a variable that stores the memory address of another variable as its value.
• A pointer variable points to a data type (like int) of the same type, and is created with the * operator. The address of the variable you're working with is assigned to the pointer:

How do you declare a pointer?

int* p;

The above statement declares a pointer ‘p’ of ‘int’ type.

int *p1;
int * p2;

The above are also different ways to declare a pointer.

How do you assign addresses to pointers?

int* pc, c;
c = 5;
pc = &c;

5 is assigned to the ‘c’ variable. The address of ‘c’ is assigned to the pointer variable ‘pc’.

How do you get the value of a pointer?

We use the * operator.

int* pc, c;
c = 5;
pc = &c;
printf("%d", *pc);   // Output: 5

To get the value stores in the ‘pc’ pointer, we use *pc. * is also called the dereference operator.