Introduction to Pointers

A pointer stores the location of another variable. It lets a function or another part of a program work with the same underlying variable instead of only a copied value.

A pointer type is written with a leading asterisk: *int is a pointer to an int. The expression &score obtains the address of score, and *ptr reads the value at that address. A Go pointer does not support arbitrary pointer arithmetic.

Go still passes pointer arguments by value: the copied pointer refers to the original variable. Focus on what is shared rather than the physical address, which is not useful for a deterministic example.

Follow this diagram before executing the example. Check where a value or decision changes what runs next.

This example is a complete program. Save it as main.go or paste it into the Go Playground.

Go code

package main

import "fmt"

func main() {
	score := 80
	ptr := &score
	fmt.Println("Score:", score)
	fmt.Println("Through pointer:", *ptr)
	*ptr = 95
	fmt.Println("Updated score:", score)
}

Output

Score: 80
Through pointer: 80
Updated score: 95

The pointer stores the address of score. Dereferencing it first reads 80; assigning 95 through the pointer changes the very same score variable, so the final print shows 95.

• *int declares a pointer type, while *ptr in an expression dereferences a pointer.
• Do not dereference a nil pointer.

Create a variable for a temperature, take its address, then update it through a pointer. Print the original variable afterwards.

Tip: Edit the example above, predict the output, and run the modified code to test your reasoning.

You have practiced Introduction to Pointers in a small, self-contained program. The important habit is to predict what runs, inspect the actual output and distinguish the language rule from the particular example.

Before continuing, make sure you can explain the program to someone who has not seen it, including the line that changes its result.