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# Character Set and Source File Encoding

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## Character Set

The syntax of Erlang tokens allows the use of the full ISO-8859-1 (Latin-1) character set. This is noticeable in the following ways:

- All the Latin-1 printable characters can be used and are shown without the escape backslash convention.
- Unquoted atoms and variables can use all Latin-1 letters.

Octal | Decimal |  | Class
--- | --- | --- | ---
200 - 237 | 128 - 159 |  | Control characters
240 - 277 | 160 - 191 | - ¿ | Punctuation characters
300 - 326 | 192 - 214 | À - Ö | Uppercase letters
327 | 215 | × | Punctuation character
330 - 336 | 216 - 222 | Ø - Þ | Uppercase letters
337 - 366 | 223 - 246 | ß - ö | Lowercase letters
367 | 247 | ÷ | Punctuation character
370 - 377 | 248 - 255 | ø - ÿ | Lowercase letters

Table: Character Classes

The following tokens are allowed to also use Unicode characters outside of the Latin-1 range:

- String literals. Example: `"√π"`
- Character literals. Example: `$∑`
- Comments in code.
- Quoted atoms. Example: `'μs'`
- Function names. Example: `'s_to_μs'(S) -> S * 1_000_000.`

Atoms used as module names, application names, and node names are restricted to the Latin-1 range.

#### Change

Support for Unicode in string literals, character literals, and comments was introduced in Erlang/OTP R16B. Support for Unicode in atom and function names was introduced in Erlang/OTP 20.

## Source File Encoding

The Erlang source file `encoding` is selected by a comment in one of the first two lines of the source file. The first string that matches the regular expression `coding\s*[:=]\s*([-a-zA-Z0-9])+` selects the encoding. If the matching string is an invalid encoding, it is ignored. The valid encodings are `Latin-1` and `UTF-8`, where the case of the characters can be chosen freely.

The default Erlang source file encoding if no valid `coding` comment is present is UTF-8.

Two examples, both selecting Latin-1 as the source file encoding:

    %% For this file we have chosen encoding = Latin-1

    %% -*- coding: latin-1 -*-

#### Change

The default encoding for Erlang source files was changed from Latin-1 to UTF-8 in Erlang/OTP 17.0.

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