What Is This Called _ On A Keyboard

Here's a comprehensive article about what the "_" symbol on a keyboard is called, its uses, and its history:

What Is This Called _ on a Keyboard?

The "_" symbol on a keyboard is called an underscore. It's a character that's been around since the early days of computing and has a variety of uses, from basic text formatting to programming. In this article, we'll explore the underscore's history, its various applications, and some tips on how to use it effectively. Whether you're a student, a writer, a programmer, or just a curious computer user, understanding the underscore is a valuable skill.

Introduction to the Underscore

The underscore character (_) is a glyph that appears as a horizontal line, typically located at the baseline of text. It is commonly found on computer keyboards and is used in various contexts within computing, writing, and other fields. While it might seem like a simple character, the underscore has a rich history and diverse range of applications.

The underscore is present on most standard keyboard layouts, usually sharing a key with the hyphen (-) or dash. It is accessed by holding down the Shift key and pressing the hyphen/underscore key. The placement can vary slightly depending on the keyboard layout (e.g., QWERTY, AZERTY), but it's generally located to the right of the zero (0) key.

History of the Underscore

The underscore's roots can be traced back to typewriters. In the pre-computer era, typewriters used the underscore as a way to underline text. Since typewriters lacked the ability to print in different fonts or styles (like italics or bold), the underscore was a simple workaround. Typists would type the word, backspace over it, and then type underscores to create the underlined effect.

With the advent of computers and digital text processing, the underscore's role evolved. While dedicated formatting options like bolding and italics became available, the underscore found new purposes in programming, file naming, and other technical contexts.

Common Uses of the Underscore

The underscore is a versatile character with many applications:

• Underlining Text (Obsolete): Historically, the underscore was used to underline text in documents where true formatting wasn't possible. However, with the advent of word processors and HTML, this use has largely been superseded by dedicated underlining features.
• Programming: In many programming languages, underscores are used in variable names and function names to improve readability.
• File Naming: Underscores are often used in file names to separate words, especially in systems where spaces are not allowed or can cause issues.
• Web Addresses (URLs): Although hyphens are generally preferred, underscores are sometimes used in URLs.
• Masking Sensitive Information: Underscores can be used to mask parts of sensitive information, such as credit card numbers or passwords.
• Placeholder: In some contexts, underscores can act as a placeholder for missing or unknown data.
• Markup and Formatting: In certain markup languages, underscores can indicate specific formatting instructions.

Underscore in Programming

In the world of programming, the underscore is far more than just a cosmetic character; it's a functional element used to enhance code readability and define variable scope. Here's a closer look at how it's used in several popular programming languages:

Python

Python makes extensive use of underscores for various purposes:

• Single Underscore Prefix (_variable): A single underscore prefix indicates that a variable or method is intended for internal use within a module. While it doesn't prevent external access, it signals to other programmers that it should be treated as a non-public part of the API.
• Double Underscore Prefix (__variable): Double underscores trigger name mangling. The Python interpreter modifies the name to make it harder (but not impossible) to access from outside the class. This is used to avoid naming conflicts in subclasses.
• Double Underscores at Beginning and End (__init__): These are used for special methods (also known as "magic methods" or "dunder methods"). Examples include __init__ (the constructor), __str__ (string representation), and __len__ (length of an object).
• Single Underscore as a Variable Name (_): A single underscore can be used as a variable name to indicate that a value is intentionally discarded. This is common in loops or when unpacking tuples where you only need some of the values.
• Numeric Literals: In Python 3.6 and later, underscores can be used to improve the readability of numeric literals:

  large_number = 1_000_000  # Represents one million
  

JavaScript

In JavaScript, the underscore is often used, though not enforced by the language itself, to denote private members of a class or object.

• Private Members: While JavaScript doesn't have true private members in the same way as some other languages (until the recent introduction of # for private class fields), a common convention is to prefix private variables and methods with an underscore. This serves as a signal to other developers that these members are intended for internal use.
• Libraries and Frameworks: Some JavaScript libraries and frameworks, such as Underscore.js (ironically), use underscores as part of their naming conventions or utility functions.

PHP

PHP also uses the underscore in a few specific contexts:

• Naming Conventions: Similar to JavaScript, underscores are often used in PHP to denote private or protected members of a class.
• Translation Functions: In many PHP frameworks and content management systems (CMS) like WordPress, the underscore is used in translation functions (e.g., _e(), __()) to mark strings for localization.

Other Languages

Many other programming languages use underscores in similar ways:

• C/C++: Underscores are often used in variable names, especially in system-level programming. A leading underscore is sometimes used to indicate implementation-specific functions or variables.
• Java: While not as common as in Python or JavaScript, underscores can be used in variable names, although the convention is to use camelCase. Single underscores are allowed as variable names but are generally discouraged.
• Swift: In Swift, the underscore can be used to ignore a parameter in a function or closure:

  func doSomething(_: Int, with value: String) {
      print(value)
  }
  

Underscore in File Naming

In file naming, the underscore serves as a practical alternative to spaces. Many operating systems and web servers handle spaces in file names poorly, requiring them to be encoded in URLs (e.g., %20) or leading to errors. Using underscores avoids these issues.

Benefits of Using Underscores in File Names:

• Compatibility: Underscores are universally accepted across different operating systems (Windows, macOS, Linux) and web servers.
• Readability: They improve readability by visually separating words in a file name.
• SEO: Search engines generally treat underscores as word separators, which can be beneficial for SEO (Search Engine Optimization) when naming image files or other web assets.

Examples:

• my_document.pdf
• image_of_a_cat.jpg
• report_2023_final.docx

Underscore in URLs

While hyphens are generally preferred for separating words in URLs for SEO purposes, underscores are sometimes used. Google treats both hyphens and underscores as word separators, so using underscores won't necessarily harm your search engine ranking. However, hyphens are generally considered more user-friendly and are more widely adopted as a best practice.

Example:

• www.example.com/category_name/product_name

Alternatives to Underscore

While the underscore is useful, there are alternatives that can be used in different contexts:

• Hyphens (-): Commonly used in URLs and file names as word separators.
• Spaces: Can be used in file names on some systems, but may cause issues with web servers and scripting.
• CamelCase: A naming convention where words are joined together, with each word after the first capitalized (e.g., myVariableName). Commonly used in programming.

How to Type an Underscore

Typing an underscore is straightforward on most keyboards:

1. Locate the Key: Find the key that has both the hyphen (-) and the underscore (_) symbols. This key is usually located to the right of the zero (0) key.
2. Use the Shift Key: Press and hold down the Shift key.
3. Press the Hyphen/Underscore Key: While holding Shift, press the hyphen/underscore key. This will produce an underscore (_).

Scientific Explanation

From a technical perspective, the underscore is represented by a specific character code in various encoding standards. In ASCII (American Standard Code for Information Interchange), the underscore is represented by the decimal value 95 (or hexadecimal 0x5F). In Unicode, the underscore is represented by U+005F.

These character codes allow computers to consistently interpret and display the underscore character across different systems and applications.

FAQ About the Underscore

• Is it OK to use underscores in URLs?
  • Yes, it is technically OK, but hyphens are generally preferred for better readability and SEO.
• Are underscores allowed in variable names?
  • Yes, in many programming languages, underscores are allowed and often used in variable names to improve readability.
• What's the difference between an underscore and a hyphen?
  • The underscore is a character that sits on the baseline, while the hyphen is typically used to connect words or parts of words. In URLs, hyphens are generally preferred for SEO.
• Why do programmers use underscores so much?
  • Programmers use underscores to improve code readability, denote private variables, and follow language-specific conventions.
• Can I use an underscore at the beginning of a file name?
  • Yes, you can, but be aware that some systems treat files with leading underscores as hidden files.
• Does Google treat underscores and hyphens the same in URLs?
  • Yes, Google treats both as word separators, but hyphens are generally recommended.
• What is the ASCII code for the underscore?
  • The ASCII code for the underscore is 95.
• What is the Unicode value for the underscore?
  • The Unicode value for the underscore is U+005F.
• What is the underscore symbol called?
  • It is called an underscore.

Conclusion

The underscore is a seemingly simple character with a surprisingly rich history and a wide range of uses. From its early days as a substitute for underlining on typewriters to its modern role in programming, file naming, and web addresses, the underscore continues to be a valuable tool for computer users and developers. Understanding its various applications and conventions can help you write cleaner code, create more compatible file names, and improve your overall digital literacy. Whether you're coding, writing, or simply organizing your files, mastering the underscore is a worthwhile endeavor.