Data Types

Introduction

Go is statically typed, meaning variables always have a specific type and that type cannot change.

Data Type for a variable defines:

• The amount of memory space allocated for variables.

• A data type specifies the possible values for variables.

• The operations that can be performed on variables.

Go built-in data types:

• Numbers

• Boolean

• String

Integer

Signed integers

Type	Size	Description (Two's complement)
int8	8 bits	8 bit signed integer
int16	16 bits	16 bit signed integer
int32	32 bits	32 bit signed integer
int64	64 bits	64 bit signed integer, can also be represented in octal and hexadecimal
int	Platform dependent	signed integers of at least 32-bit in size, not equivalent to int32.

Unsigned integers

Type	Size	Description (Two's complement)
uint8	8 bits	8 bit unsigned integer
uint16	16 bits	16 bit unsigned integer
uint32	32 bits	32 bit unsigned integer
uint64	64 bits	64 bit unsigned integer
uint	Platform dependent	unsigned integers of at least 32-bit in size, not equivalent to int32.

Use int unless for specific reasons for others. Integral types have default value of 0. Octal numbers can be declared using prefix and hexadecimal using the 0x prefix.

Other integer types

Type	Description (Two's complement)
byte	It is alias for and equivalent to uint8
rune	It is alias for and equivalent to int32, used to represent characters.
uintptr	It is used to hold memory address pointers

Golang does not support a char data type, instead it has byte and rune to represent character values. This helps to distinguish characters from integer values. byte data type is represented with a ASCII value and the rune data type is represented with Unicode value encoded in UTF-8 format.

package main
import "fmt"
 
func main() {
 var varByte byte = 'a' // ASCII value of 97
 var varRune rune = '♥' // Unicode value of U+2665
 
 fmt.Printf("%c = %d and %c = %U\n", varByte, varByte, varRune, varRune)
}

a = 97 and ♥ = U+2665

Float

Go supports float32 and float64 represented with 32-bit and 64-bit in memory respectively.

var num1 float32 = 20.0320
var num2 = 20.0818 // Type inferred as float64

Complex Numbers

Go supports complex64 and complex128. Each of the type uses float32 and float64 respectively, to represent their real and imaginary parts.

var num1 = 3 + 7i  // Type inferred as complex128

Boolean

var flag = true

String

// No newlines, and can contain escape sequences like \n, \t
var fstr="Hello World"
 
// Can span multiple lines. Escape characters are not allowed.
var sstr= `Hello world, this
a multi-line text string.`

Type Conversions

Syntax: The expression T(v) converts the value v to the type T.

var i int = 42
var f float64 = float64(i)
var u uint = uint(f)

// short syntax
i := 42
f := float64(i) // 42.000000
u := uint(f)

Type Inference

When declaring a variable without specifying an explicit type (either by using the := syntax or var = expression syntax), the variable's type is inferred from the value on the right hand side.

package main

import "fmt"

func main() {
	i := 42
	f := 12.0212
	c := 0.5 + 2i
	fmt.Printf("i is of type %T\n", i)
	fmt.Printf("f is of type %T\n", f)
	fmt.Printf("c is of type %T\n", c)
}

i is of type int
f is of type float64
c is of type complex128