Go — Data Types

Basic types

Type	Description
bool	true or false
string	UTF-8 text
int, int8, int16, int32, int64	Signed integers
uint, uint8, uint16, uint32, uint64	Unsigned integers
float32, float64	Floating point
complex64, complex128	Complex numbers
byte	Alias for uint8
rune	Alias for int32 (Unicode code point)

Numeric types

package main

import "fmt"

func main() {
    var i int = 42
    var f float64 = 3.14
    var u uint = 42
    var b byte = 255
    var r rune = 'A'

    fmt.Println(i, f, u, b, r)
}

Strings

package main

import "fmt"

func main() {
    s := "Hello, World!"
    raw := `Raw string
with newlines`
    utf8 := "UTF-8: 你好世界"

    fmt.Println(s)
    fmt.Println(raw)
    fmt.Println(utf8)
    fmt.Println(len(s))        // 13
    fmt.Println(s[0:5])        // Hello
    fmt.Println(s + " Bye")    // Hello, World! Bye
}

Arrays

package main

import "fmt"

func main() {
    var arr [5]int
    arr[0] = 10
    arr[1] = 20

    fruits := [3]string{"Apple", "Banana", "Cherry"}

    fmt.Println(arr)    // [10 20 0 0 0]
    fmt.Println(fruits) // [Apple Banana Cherry]
    fmt.Println(len(arr)) // 5
}

Slices

package main

import "fmt"

func main() {
    nums := []int{1, 2, 3, 4, 5}
    slice := nums[1:3] // [2, 3]

    fmt.Println(nums)  // [1 2 3 4 5]
    fmt.Println(slice) // [2 3]

    // Append
    nums = append(nums, 6, 7)

    // Make
    data := make([]int, 5, 10) // len=5, cap=10
    fmt.Println(data)
}

Maps

package main

import "fmt"

func main() {
    ages := map[string]int{
        "Alice": 30,
        "Bob":   25,
    }

    ages["Charlie"] = 35
    delete(ages, "Bob")

    fmt.Println(ages)

    // Check if key exists
    age, ok := ages["Alice"]
    if ok {
        fmt.Println("Alice:", age)
    }
}

Structs

package main

import "fmt"

type Person struct {
    Name string
    Age  int
}

func main() {
    p1 := Person{Name: "Alice", Age: 30}
    p2 := Person{"Bob", 25} // Positional

    fmt.Println(p1.Name)
    fmt.Println(p2)
}

Pointers

package main

import "fmt"

func increment(x *int) {
    *x++
}

func main() {
    x := 10
    increment(&x)
    fmt.Println(x) // 11
}

Type conversion

package main

import (
    "fmt"
    "strconv"
)

func main() {
    // Numeric conversion
    var i int = 42
    var f float64 = float64(i)
    var u uint = uint(f)

    fmt.Println(i, f, u)

    // String conversion
    s := strconv.Itoa(i)  // "42"
    n, _ := strconv.Atoi("42") // 42

    fmt.Println(s, n)
}

Mini Practice

Write Go code that:

1. Declares variables of each basic type
2. Creates a slice and appends elements
3. Creates a map and iterates with range
4. Defines a struct with fields and methods

Up Next

In the next lesson, you'll learn about Operators — arithmetic and logical operations.