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Zero value

Learn that every type in Go has a zero value.

Zero value

In Go every type has a zero value. When a variable is declared without an explicit value, it gets this zero value. This prevents 'undefined behaviour' issues.

For numeric types the zero value is 0, for bool false, for string "" (empty), for pointer and interface nil.

This behaviour makes Go safe; no variable starts with 'garbage'. When a new struct is created, all its fields take their zero values.

Zero value table

Zero values of common types:

  • int, float64: 0
  • bool: false
  • string: ""
  • pointer, slice, map, interface: nil
  • struct: each field's zero value

This table is often consulted in daily coding. Knowing zero values matters especially when checking struct fields.

Practice Zero values

Declare var n int, var f float64, var s string and var b bool without values. Print them with fmt.Printf("%d %g %q %t\n", n, f, s, b).

Starter code

main.go
package main

import "fmt"

func main() {
    // buraya yaz
}

Sample solution

main.go
package main

import "fmt"

func main() {
    var n int
    var f float64
    var s string
    var b bool
    fmt.Printf("%d %g %q %t\n", n, f, s, b)
}

Expected output

0 0 "" false

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What is the zero value of a string variable?

  • nil
  • 0
  • empty string ("")
  • false Correct answer

Explanation: The zero value of string is the empty string.

2 Bool zero value

Question 
The zero value of a bool variable: ____
Answer 
The zero value of a bool variable: false

Explanation: The zero value of bool is false.

3 Match the zero values

Term Meaning
int 0
bool false
string empty
pointer nil

All lessons in Beginner

1 Go basics

  1. What is Go?
  2. Installing Go
  3. Your first program
  4. go run and go build
  5. Comments and semicolons
  6. Summary - Go basics

2 Modules

  1. go mod init
  2. package and import
  3. The main package
  4. Multiple files
  5. go.sum and dependencies
  6. Summary - Modules

3 Variables

  1. Declaration with var
  2. Short declaration :=
  3. const and iota
  4. Zero value
  5. Type inference
  6. Summary - Variables

4 Data types

  1. int and float
  2. bool and string
  3. byte and rune
  4. Type conversion
  5. Type definitions
  6. Summary - Data types

5 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. Command-line menu

6 Functions

  1. func declaration
  2. Parameters and return
  3. Multiple return
  4. Variadic functions
  5. Anonymous functions
  6. Summary - Functions

7 Control flow

  1. if, else if, else
  2. for loop
  3. Iterating with range
  4. switch and fallthrough
  5. break and continue
  6. Summary - Control flow

8 Array and slice

  1. Array declaration
  2. Slice declaration
  3. Appending with append
  4. Sub-slice
  5. len and cap
  6. Summary - Array and slice

9 Project: Shopping cart

  1. Product struct
  2. Adding to cart
  3. Computing total
  4. Printing the cart

10 Map

  1. Map declaration
  2. Adding elements
  3. Looking up in a map
  4. Deleting from a map
  5. Iterating a map with range
  6. Summary - Map

11 String

  1. String and byte
  2. String concatenation
  3. Conversion with strconv
  4. The strings package
  5. Rune and UTF-8
  6. Summary - String

12 Pointer

  1. What is a pointer?
  2. & and * operators
  3. The new function
  4. Pointers and functions
  5. Nil pointer
  6. Summary - Pointer

13 Struct

  1. Struct declaration
  2. Creating a struct
  3. Field access
  4. Struct embedding
  5. Struct and pointer
  6. Summary - Struct

14 Methods

  1. Method declaration
  2. Pointer receiver
  3. Value receiver
  4. Methods and embedding
  5. Method chaining
  6. Summary - Methods

15 Interface and error

  1. Interface declaration
  2. Implicit satisfaction
  3. The error interface
  4. Returning errors
  5. errors.Is and errors.As
  6. Summary - Interface and error

16 Beginner final

  1. Challenge 1 - Combined program
  2. Challenge 2 - Data structure
  3. Challenge 3 - Error handling
  4. Challenge 4 - Mini app