Integers: whole numbers are our friends

Syntax:

let x = wholeNumber // implicit Integer constant
var y = wholeNumber // implicit Integer variable

let x: Int = wholeNumber // explicit Integer constant
var y: Int = wholeNumber // explicit Integer variable

An integer is a whole number within the range of -2,147,483,648 and 2,147,483,647. When specifying a whole number as the value of a constant or variable, Swift will automatically assume the type of Int. However, you can explicitly declare a constant or variable to be an Integer.

let x = 10 // declare a constant as an implicit Integer with a value of 10
var y = 20 // declare a variable as an implicit Integer with a value of 10
var z = x + y // declare a variable as an implicit Integer with a value of x+y (30)
var a,b,c : Int // declare multiple variables explicitly as Integers