What is a pointer?
- Go course
- Beginner
- Lesson 63/90
- 4 min
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 changedGo 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.
Practice 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.
Starter code
package main
import "fmt"
func main() {
// buraya yaz
}Sample solution
package main
import "fmt"
func main() {
x := 10
p := &x
*p = *p * 3
fmt.Println(x, *p)
}Expected output
30 30
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Right after <code>var p *int</code> is declared, what is <code>p</code>'s value?
- A compile error
- nil Correct answer
- 0
- A random address
Explanation: The zero value of a pointer is nil; it doesn't point at anything yet.
2 Value at the address
x := 5
p := &x
fmt.Println(____p) // 5x := 5
p := &x
fmt.Println(*p) // 5Explanation: *p reads the value the pointer points to.
3 Expression and meaning
| Term | Meaning |
|---|---|
*int |
Pointer-to-int type |
&x |
Address of x |
*p |
Value at the address |
nil |
Empty pointer |