> ## Documentation Index
> Fetch the complete documentation index at: https://docs.abbyy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Alphabet used in regular expressions

> Reference guide for regular expression syntax used in ABBYY Vantage Scanning Station.

Scanning Station uses a custom regular-expression alphabet for validating registration-parameter values. The tokens below describe the available syntax.

| Name | Conventional designation | Usage example |
| :- | :- | :- |
| Any character | `*` | `` `"c"*"t"` `` allows words like `cat`, `cot`, etc. |
| Letter | `C` | `` `C"ot"` `` allows words like `Rot`, `pot`, `cot`, `Dot`, `mot`, etc. |
| Uppercase letter | `A` | `` `A"ot"` `` allows words like `Rot`, `Cot`, `Mot`, `Dot`, etc. |
| Lowercase letter | `a` | `` `a"ot"` `` allows words like `rot`, `cot`, `mot`, `dot`, etc. |
| Letter or number | `X` | `` `X` `` allows any standalone number or letter. |
| Number | `N` | `` `N"th"` `` allows words like `5th`, `4th`, `6th`, etc. |
| String | `" "` | `` `"cot"` `` |
| Or | `\|` | `` `"pl"("o"\|"a")"t"` `` allows `"plot"` and `"plat"`. |
| Character from group | `[]` | `` `[tm]"ot"` `` allows `"tot"` and `"mot"`. |
| Character not from group | `[^]` | `` `[^t]"ot"` `` allows `"cot"`, `"lot"`, etc., but not `"tot"`. |
| Space (within group) | `\s` | `` `[A\s]` `` allows only the letter `A` or a space. |
| Any number of repetitions | `{-}` | `` `[AB74]{-}` `` allows any combination of `A`, `B`, `7`, `4` of any length. |
| Exactly n repetitions | `{n}` | `` `N{2}"th"` `` allows `25th`, `84th`, `11th`, etc. |
| From n to m repetitions | `{n-m}` | `` `N{1-3}"th"` `` allows `5th`, `84th`, `111th`, etc. |
| From 0 to n repetitions | `{-n}` | `` `N{-2}"th"` `` allows `84th`, `5th`, etc. |
| n or more repetitions | `{n-}` | `` `N{2-}"th"` `` allows `25th`, `834th`, `311th`, `34576th`, etc. |
| Subexpression | `()` | — |
| Hyphen symbol | `[\-]` | — |
| Slash symbol | `[\\]` | — |

## Examples of regular expressions

| Purpose | Pattern | Sample values |
| :- | :- | :- |
| Postal code | `[0-9]{6}` | `142172` |
| Zip code (USA) | `[0-9]{5}("-"[0-9]{4}){-1}` | `55416`, `33701-4313` |
| Income | `N{4-8}[,]N{2}` | `15000,00`, `4499,00` |
| Month (numerical) | `((\|"0")[1-9])\|("10")\|("11")\|("12")` | `4`, `05`, `12` |
| Fraction | `("-"\|)([0-9]{1-})(\|((".",")([0-9]{1-})))` | `1234,567`, `0.99`, `100,0`, `-345.6788903` |
| Email | `[A-Za-z0-9_]{1-}((".""-")[A-Za-z0-9_]{1-}){-3}"@"[A-Za-z0-9_]{1-}((".""-")[A-Za-z0-9_]{1-}){-4}"."([A-Za-z]{2-4}\|"asia"\|"museum"\|"travel"\|"example"\|"localhost")` | `support@abbyy.com`, `my-name@company.org.ru`, `info@gallery.museum` |

## Related topics

* [Registration parameters in batches](/vantage/documentation/scanning-station/interface/registration-params-batches)
* [Registration Parameters window](/vantage/documentation/scanning-station/interface/registration-params-window)
* [Index documents manually](/vantage/documentation/scanning-station/operator/index-manually)
* [Appendix](/vantage/documentation/scanning-station/appendix/appendix)