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Term Definition

The underscore [ _ ] (also called understrike, underbar, or underline) is a character that originally appeared on the typewriter and was primarily used to underline words.

The underscore ( _ ) is also known as an understrike, underbar, or underline, and is a character that was originally on a typewriter keyboard and was used simply to underline words or numbers for emphasis. Today, the character is used to create visual spacing in a sequence of words where whitespace is not permitted. The most common instance of this is in computer file names and titles, email addresses, and Internet URLs. Some computer programming automatically underlines a word or sentence that begins with an underscore or ends with an underscore.

Rules when using underscores

Underscoring is used in a variety of ways in communication, both through the Internet and in handwriting methods. It has become very frequently used in computer communications (just like the @ sign in email addresses) in recent decades because it provides another varietal when one commonly-used version of an email address or internet name is already taken. If you buy essay samples from us, you'll likely receive a file with underscores in the name.

Here is an example of a computer file name of a history paper using underscoring instead of spaces which is more easily read by computer programs:


Here is an example of an email address using underscoring, which might be used when a more common version of the address is already taken:


Here is an example of an Internet URL using underscoring:


Here is an example of what an underlined text might look like if input in code into computer programming software:


Some computer programming automatically underlines a word or sentence that begins with an underscore or ends with an underscore.

Uses in other disciplines

The underscore should not be confused with the dash character, and a series of underscores may be used to create a blank line for a form; keep in mind that the line may have tiny breaks that will be visible should the text or font be made larger at any point in time. The underscore can be used to create a horizontal line by typing a blank line and then changed the orientation of the screen image or paper. Hyphens and dashes are related to the underscore, but vary greatly in their applications to written communications.

The underscore is also used as a diacritic mark in certain languages, most notably those from the Egyptian family of languages. These languages include Egyptian, languages used in Gabon, Izere spoken and written in Nigeria, and some American Indian languages such as Shoshoni and Kiowa.

The first IBM character-coding system was introduced in 1964 and used a small character set, of which the underscore was one character. It was referred to at that time as the “break character” because it broke up simple lines of text and code, as in “rate_of_pay”. By 1967, the underscore character was also used in ASCII, an early computer programming language.

It is common in computer programming to use an underscore just before the name of a file intended for internal use within a computer library, or for a header file. Ruby, Perl, and Windows PowerShell also use underscores after certain characters to create a special variable.

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Synonyms: underscore

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