1. Writing Functions
2. Accepting Parameter
3. Returning Values
4. Parameter Labels
5. Omitting Parameter Labels
6. Default Parameters
7. Variadic Functions
8. Throwing Functions
9. Inout Parameters

1. Writing Functions

func printNum() {
    for num in 1...4 {
        print(num)
    }
}

printNum()

output

1 2 3 4

2. Accepting Parameter

func square(number: Int) {
    print("Square of \(number) is", number * number)
}

square(number: 3)

output

Square of 3 is 9