Autocomplete

Autocomplete is a feature provided by many web browsers, e-mail programs, search engine interfaces, source code editors, database query tools, word processors, and command line interpreters. Autocomplete involves the program predicting a word or phrase that the user wants to type in without the user actually typing it in completely. This feature is effective when it is easy to predict the word being typed based on those already typed, such as when there are a limited number of possible or commonly used words (as is the case with e-mail programs, web browsers, or command line interpreters), or when editing text written in a highly-structured, easy-to-predict language (as in source code editors). Autocomplete speeds up human-computer interactions in environments to which it is well suited. Autocomplete features are often enabled by default, and disabling or defeating them can sometimes be difficult for users to accomplish.

In web browsers

In web browsers, autocomplete is done in the address bar (using items from the browser's history) and in text boxes on frequently used pages, such as a search engine's search box. Autocomplete for web addresses is particularly convenient because the full addresses are often long and difficult to type correctly.

In e-mail programs

In e-mail programs autocomplete is typically used to fill in the e-mail addresses of the intended recipients. Generally, there are a small number of frequently used e-mail addresses, hence it is relatively easy to use autocomplete to select between them. Like web addresses, e-mail addresses are often long, hence typing them completely is inconvenient.

For instance,

• Microsoft Outlook Express will find addresses based on the name that is used in the address book. Google's Gmail will find addresses by any string that occurs in the address or stored name.
• BBDB^[1] runs in emacs.

In search engines

In search engines, autocomplete user interface features provide users with suggested queries or results as they type their query in the search box. This is also commonly called autosuggest or incremental search. This type of search often relies on matching algorithms that forgive entry errors such as phonetic Soundex algorithms or the language independent Levenshtein algorithm. The challenge remains to search large indices or popular query lists in under a few milliseconds so that the user sees results pop up while typing.

In source code editors

Autocomplete of source code is also known as code completion. In a source code editor autocomplete is greatly simplified by the regular structure of the programming languages. There are usually only a limited number of words meaningful in the current context or namespace, such as names of variables and functions. An example of code completion is the Microsoft's IntelliSense design. It involves showing a pop-up list of possible completions for the currently input prefix to allow the user to choose the right one. This is particularly useful in object-oriented programming because often the programmer will not know exactly what members a particular class has. Therefore, autocomplete then serves as a form of convenient documentation as well as an input method. Another beneficial feature of autocomplete for source code is that it encourages the programmers to use longer, more descriptive variable names incorporating both lower and upper case letters (CamelCase), hence making the source code more readable. Typing large words with many mixed cases like "numberOfWordsPerParagraph" can be difficult, but Autocomplete allows one to complete typing the word using a fraction of the keystrokes.

In database query tools

Autocompletion in database query tools allows the user to autocomplete the table names in an SQL statement and column names of the tables referenced in the SQL statement. As text is typed into the editor, the context of the cursor within the SQL statement provides an indication of whether the user needs a table completion or a table column completion. The table completion provides a list of tables available in the database server the user is connected to. The column completion provides a list of columns for only tables referenced in the SQL statement. Aqua Data Studio and SQL Server Management Studio are applications that provide autocomplete in query tools.

In word processors

In many word processing programs, autocompletion decreases the amount of time spent typing repetitive words and phrases. The source material for autocompletion is either gathered from the rest of the current document or from a list of common words defined by the user. Currently OpenOffice.org, StarOffice, Microsoft Office, and KOffice include support for this kind of autocompletion, as do advanced text editors such as Emacs and Vim.

In command-line interpreters

Main article: Command-line completion

In a command-line interpreter, such as Unix's sh or bash, or Windows's cmd.exe or PowerShell, or in similar command line interfaces, autocomplete of command names and file names may be accomplished by keeping track of all the possible names of things the user may access. Here autocomplete is usually done by pressing the Tab ⇆ key after typing the first several letters of the word. For example, if the only file in the current directory that starts with x is xLongFileName, the user may prefer to type x and autocomplete to the complete name. If there were another file name or command starting with x in the same scope, the user would type more letters or press the Tab key repeatedly to select the appropriate text.

Standalone tools

There are standalone tools that add similar functionality to existing applications. These programs monitor user keystrokes and complete a word based on first typed letters in context with previous letters.

Similar tools

Autoreplace is a somewhat related feature that involves automatic replacement of a particular string with another one, usually one that is longer and harder to type, as "myname" with "Lee John Nikolai François Al Rahman". This can also quietly fix simple typing errors, such as turning "teh" into "the".

See also

• Autofill
• Incremental search
• Snippet
• Context sensitive user interface
• Combo box
• Search suggest drop-down list

Notes

1. ^ "The Insidious Big Brother Database". http://bbdb.sourceforge.net/. Retrieved 2008-02-23. 

External links

• A brief discussion on the history of code completion
• Live Search Explained -- Examples and explanations of working web examples plus a discussion of the usability benefits compared to traditional search