#### Basic Data Types:

Swift provides a rather large number of types. However, you can write perfectly good programs using only four of those:

Here are some examples of declaring and initializing variables:

```
var age: Int = 28
var price: Double = 8.99
var message: String = "Game Over"
var lateToWork: Bool = true
```

#### Naming Constants and Variables:

Constant and variable names can contain almost any character, including Unicode characters:

```
let π = 3.14159
let 你好 = "你好世界"
let = "happy"
```

Constant and variable names can’t contain whitespace characters, mathematical symbols, arrows, private-use Unicode scalar values, or line- and box-drawing characters. Nor can they begin with a number, although numbers may be included elsewhere within the name.

#### Numeric Type Conversion:

A type cast is basically a conversion from one type to another.

The notation `(Type)value`

means “convert `value`

to `Type`

“. So for example:

```
double weight1;
int weight2;
weight1 = 154.49;
weight2 = (int) weight1;
// weight2 is now 154
```

**Note:** Going from a `double`

to an `int`

simply removes the decimal. There’s no rounding involved.