# Strings and Characters

Strings are collections of characters. Strings have the type `String`, and characters have the type `Character`. Strings can be used to work with text in a Unicode-compliant way. Strings are immutable.

String and character literals are enclosed in double quotation marks (`"`).

```
let someString = "Hello, world!"
```

String literals may contain escape sequences. An escape sequence starts with a backslash (`\`):

* `\0`: Null character
* `\\`: Backslash
* `\t`: Horizontal tab
* `\n`: Line feed
* `\r`: Carriage return
* `\"`: Double quotation mark
* `\'`: Single quotation mark
* `\u`: A Unicode scalar value, written as `\u{x}`,

  where `x` is a 1–8 digit hexadecimal number

  which needs to be a valid Unicode scalar value,

  i.e., in the range 0 to 0xD7FF and 0xE000 to 0x10FFFF inclusive

```
// Declare a constant which contains two lines of text
// (separated by the line feed character `\n`), and ends
// with a thumbs up emoji, which has code point U+1F44D (0x1F44D).
//
let thumbsUpText =
    "This is the first line.\nThis is the second line with an emoji: \u{1F44D}"
```

The type `Character` represents a single, human-readable character. Characters are extended grapheme clusters, which consist of one or more Unicode scalars.

For example, the single character `ü` can be represented in several ways in Unicode. First, it can be represented by a single Unicode scalar value `ü` ("LATIN SMALL LETTER U WITH DIAERESIS", code point U+00FC). Second, the same single character can be represented by two Unicode scalar values: `u` ("LATIN SMALL LETTER U", code point U+0075), and "COMBINING DIAERESIS" (code point U+0308). The combining Unicode scalar value is applied to the scalar before it, which turns a `u` into a `ü`.

Still, both variants represent the same human-readable character `ü`.

```
let singleScalar: Character = "\u{FC}"
// `singleScalar` is `ü`
let twoScalars: Character = "\u{75}\u{308}"
// `twoScalars` is `ü`
```

Another example where multiple Unicode scalar values are rendered as a single, human-readable character is a flag emoji. These emojis consist of two "REGIONAL INDICATOR SYMBOL LETTER" Unicode scalar values.

```
// Declare a constant for a string with a single character, the emoji
// for the Canadian flag, which consists of two Unicode scalar values:
// - REGIONAL INDICATOR SYMBOL LETTER C (U+1F1E8)
// - REGIONAL INDICATOR SYMBOL LETTER A (U+1F1E6)
//
let canadianFlag: Character = "\u{1F1E8}\u{1F1E6}"
// `canadianFlag` is `🇨🇦`
```


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