C Memory Addresses and Pointers

Memory Addresses

Every variable in C is stored at a memory address. You can find that address using the & operator.

Pointer Basics

A pointer is a variable that holds the memory address of another variable. A pointer is declared with *

Pointer Declaration and Initialization

To declare a pointer: int *ptr;

To assign it the address of a variable: ptr = &x;

Dereferencing

Dereferencing a pointer means accessing the value at the memory location it points to. Use *ptr to do this.

Pointer Reassignment

Pointers can be reassigned to point to different variables, as long as types match.

Printing Pointer Addresses

Use %p with printf() to print pointer addresses.

p vs. *p

• p holds the memory address to which it is assigned to
• *p points to the content that is held in the memory address which it is assigned to

Changing Values Using Pointers

You can use pointers to modify a variable's value by referencing its memory address. This is useful for updating values inside functions or performing direct memory manipulation.

• *ptr is used to dereference the pointer and access/change the value.
• &var is used to get the address of a variable.

Practice Question

What will this print?

A. Address of x

B. 10

C. Error

int x = 10;
int *ptr = &x;
printf("%d", *ptr);

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