Pointers

Learn memory addresses with pointers like int*.

What is a pointer (int*)?

A pointer holds the memory address of a variable. In C#, int* p; declares p as a pointer to an integer. &x takes the address of x and *p (dereference) reads or writes the value at that address.

Pointers are valid only inside unsafe blocks and cannot directly reference managed types such as string or object. This boundary keeps GC object movement safe.

Dereference and pointer arithmetic

Accessing the value at the address held by a pointer is called dereference, written *p. *p = 20; writes 20 to that address; int v = *p; reads it.

Pointer arithmetic is also possible: p + 1 advances to the next int address (4 bytes forward). This is handy for fast loops over arrays and yields performance gains.

Exercise Print a value via a pointer

Mark Main as unsafe. Declare int a = 7;, take its address with int* p = &a; and print the value with Console.WriteLine(*p);.

Show example solution

unsafe static void Main() { int a = 7; int* p = &a; Console.WriteLine(*p); }
Example solution:
using System;

class Program
{
    unsafe static void Main()
    {
        int a = 7;
        int* p = &a;
        Console.WriteLine(*p);
    }
}

Test yourself

Pointer declaration

int x = 5;
____ p = &x;

Show answer

int x = 5;
int* p = &x;

What does *p do?
- Takes the address of p
- Reads/writes the value at the address p points to
- Creates a new pointer
- Deletes p
Show answer

Reads/writes the value at the address p points to — Correct. *p (dereference) accesses the value at the address.
Match the pointer syntax

&x

Address of x
*p

Dereference
int*

Pointer to int type
p + 1

Next int address

Next lesson: fixed statement

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