What is a pointer?

Learn that a pointer is a memory address.

What is a pointer?

A pointer is a variable that holds the memory address of another variable. The type *int means "the address of an int". With a pointer you can reach and change the same value from several places.

x := 10
p := &x          // p holds x's address
fmt.Println(*p)   // 10: the value at the address
*p = 20
fmt.Println(x)    // 20: x changed

Go has no pointer arithmetic (you can't do p++ as in C); this prevents most memory bugs.

When to use pointers

Pointers are used in two cases: when a function must change the caller's variable, and when you want to share a large value without copying it. For small values (numbers, small structs) a copy is usually simpler and faster. Slices, maps and channels already carry a reference inside; they rarely need pointers.

Exercise Change through a pointer

Declare x := 10 and take p := &x. Triple x with *p = *p * 3 and print x and *p on one line.

Show example solution

package main

import "fmt"

func main() {
    x := 10
    p := &x
    *p = *p * 3
    fmt.Println(x, *p)
}

Test yourself

Right after <code>var p *int</code> is declared, what is <code>p</code>'s value?
- A compile error
- nil
- 0
- A random address
Show answer

nil — The zero value of a pointer is nil; it doesn't point at anything yet.

Value at the address

x := 5
p := &x
fmt.Println(____p)  // 5

Show answer

x := 5
p := &x
fmt.Println(*p)  // 5

Expression and meaning

*int

Pointer-to-int type
&x

Address of x
*p

Value at the address
nil

Empty pointer

Next lesson: & and * operators

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