ASCII Character _Underscore
An underscore, _, also called an underline, low line or low dash, is a line drawn under a segment of text. In proofreading, underscoring is a convention that says "set this text in italic type", traditionally used on manuscript or typescript as an instruction to the printer. The underscore character, _, originally appeared on the typewriter and was primarily used to emphasise words as in the proofreader's convention. In modern usage, underscoring is achieved by markup or with combining characters. The original free-standing underscore character continues in use to create visual spacing within a sequence of characters, where a whitespace character is not permitted (e.g., in computer filenames, email addresses, and in Internet URLs).