# Variables

### Variables

A variable refers to a storage location in the computer’s memory that one can set aside to save, retrieve, and manipulate data.

`var score = 0`

### Constants

Constants refer to fixed values that a program may not alter during its execution. One can be declared by using the `let` keyword.

`let pi = 3.14`

### Arithmetic Operators

Swift supports arithmetic operators for:

• `+` addition
• `-` subtraction
• `*` multiplication
• `/` division
• `%` remainder
```var x = 0
x = 4 + 2  // x is now 6x = 4 - 2  // x is now 2x = 4 * 2  // x is now 8x = 4 / 2  // x is now 2x = 4 % 2  // x is now 0```

### Types

Type annotation can be used during declaration.

The basic data types are:

• `Int`: integer numbers
• `Double`: floating-point numbers
• `String`: a sequence of characters
• `Bool`: truth values
```var age: Int = 28
var price: Double = 8.99
var message: String = "good nite"
var lateToWork: Bool = true```

### String Interpolation

String interpolation can be used to construct a `String` from a mix of variables, constants, and others by including their values inside a string literal.

```var apples = 6
print("I have \(apples) apples!")
// Prints: I have 6 apples!```

### Compound Assignment Operators

Compound assignment operators provide a shorthand method for updating the value of a variable:

• `+=` add and assign the sum
• `-=` subtract and assign the difference
• `*=` multiply and assign the product
• `/=` divide and assign the quotient
• `%=` divide and assign the remainder
```var numberOfDogs = 100numberOfDogs += 1
print("There are \(numberOfDogs) dalmations!")
// Prints: There are 101 dalmations!```