Variables and Types

Go is a statically typed language — every variable has a type known at compile time. This lesson covers Go's basic types, variable declarations, zero values, type inference, constants, and type conversions.

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Basic Types

Go provides a rich set of built-in types:

Numeric Types

Type	Size	Range / Description
int8	8 bits	-128 to 127
int16	16 bits	-32,768 to 32,767
int32	32 bits	-2.1 billion to 2.1 billion
int64	64 bits	-9.2 quintillion to 9.2 quintillion
int	Platform-dependent	32 or 64 bits (most common)
uint8 (byte)	8 bits	0 to 255
uint16	16 bits	0 to 65,535
uint32	32 bits	0 to 4.2 billion
uint64	64 bits	0 to 18.4 quintillion
float32	32 bits	IEEE-754 single precision
float64	64 bits	IEEE-754 double precision (most common)
complex64	64 bits	Complex number with float32 parts
complex128	128 bits	Complex number with float64 parts

Other Built-in Types

Type	Description
bool	true or false
string	Immutable sequence of bytes (UTF-8)
byte	Alias for uint8
rune	Alias for int32 — represents a Unicode code point
error	Built-in interface for error values

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Variable Declarations

Go offers several ways to declare variables:

1. Full Declaration

var name string = "Alice"
var age int = 30
var active bool = true

2. Type Inference (omit the type)

var name = "Alice"   // inferred as string
var age = 30         // inferred as int
var pi = 3.14        // inferred as float64

3. Short Variable Declaration (inside functions)

name := "Alice"
age := 30
pi := 3.14

The := operator declares and assigns in one step. It can only be used inside functions.

4. Multiple Variables

var x, y, z int = 1, 2, 3

// Or with short declaration:
a, b, c := "hello", true, 42

5. Grouped Declaration

var (
    name   string = "Alice"
    age    int    = 30
    active bool   = true
)

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Zero Values

In Go, every variable is initialised to its zero value if no value is provided:

Type	Zero Value
int, float64, etc.	0
bool	false
string	"" (empty string)
Pointer, slice, map, channel, function, interface	nil

var count int      // 0
var name string    // ""
var active bool    // false
var data []byte    // nil