Webopedia on Google+Webopedia on TwitterWebopedia on FacebookTech Bytes Blog
Main » TERM » E »

extension

(1) An extra feature added to a standard programming language or system.

(2) In DOS and some other operating systems, one or several letters at the end of a filename. Filename extensions usually follow a period (dot) and indicate the type of information stored in the file. For example, in the filename EDIT.COM, the extension is COM, which indicates that the file is a command file. (Depending on the operating system, the punctuation separating the extension from the rest of the filename may or may not be considered part of the extension itself.)

Also see Data Formats and Their File Extensions in the Quick Reference section of Webopedia.

(3) In Macintosh environments, a program that extends the system's capabilities. When they reside in the Extensions folder, extensions are loaded into memory when the system starts. On older Macs (System 6 and earlier), extensions were called inits.

(4) Same as plug-in.







TECH RESOURCES FROM OUR PARTNERS
LATEST ARTICLES
Slideshow: 5 Hot Holiday Gifts for Tech Enthusiasts

From cute electronic toys to VR gaming, here are 5 hot gifts to give to your special tech enthusiast this holiday season. Read More »

What's Hot in Tech: AI Tops the List

Like everything in technology, AI touches on so many other trends, like self-driving cars and automation, and Big Data and the Internet of Things... Read More »

DevOp's Role in Application Security

As organizations rush to release new applications, security appears to be getting short shrift. DevSecOps is a new approach that holds promise. Read More »

STUDY GUIDES
Java Basics, Part 1

Java is a high-level programming language. This guide describes the basics of Java, providing an overview of syntax, variables, data types and... Read More »

Java Basics, Part 2

This second Study Guide describes the basics of Java, providing an overview of operators, modifiers and control Structures. Read More »

The 7 Layers of the OSI Model

The Open System Interconnection (OSI) model defines a networking framework to implement protocols in seven layers. Use this handy guide to compare... Read More »