Computer Definition

Technically, a computer is a programmable machine. This means it can execute a programmed list of instructions and respond to new instructions that it is given. Today, however, the term is most often used to refer to the desktop and laptop computers that most people use. When referring to a desktop model, the term "computer" technically only refers to the computer itself -- not the monitor, keyboard, and mouse. Still, it is acceptable to refer to everything together as the computer. If you want to be really technical, the box that holds the computer is called the "system unit."

Some of the major parts of a personal computer (or PC) include the motherboard, CPU, memory (or RAM), hard drive, and video card. While personal computers are by far the most common type of computers today, there are several other types of computers. For example, a "minicomputer" is a powerful computer that can support many users at once. A "mainframe" is a large, high-powered computer that can perform billions of calculations from multiple sources at one time. Finally, a "supercomputer" is a machine that can process billions of instructions a second and is used to calculate extremely complex calculations.

Windows Definition

Microsoft Windows is the most popular operating system for personal computers. There are several versions of the Windows operating system, including Windows XP (for home users) and Windows 2000 (for professional users). Earlier versions of Windows include Windows 3.1, 95, 98, ME, and NT. All Windows platforms use a graphical user interface (GUI), like the Mac OS, and also offer a command-line interface for typing text commands.

Linux Definition

Linux (pronounced "lih-nux", not "lie-nux") is a Unix-like operating system (OS) created by Linus Torvalds. He developed Linux because he wasn't happy with the currently available options in Unix and felt he could improve it. So he did what anybody else would do, and created his own operating system.

When Linus finished building a working version of Linux, he freely distributed the OS, which helped it gain popularity. Today, Linux is used by millions of people around the world. Many computer hobbyists (a.k.a. nerds) like the operating system because it is highly customizable. Programmers can even modify the source code and create their own unique version of the Linux operating system.

Web hosting companies often install Linux on their Web servers because Linux-based servers are cheaper to set up and maintain than Windows-based servers. Since the Linux OS is freely distributed, there are no licensing fees. This means Linux servers can host hundreds or even thousands of websites at no additional cost. Windows servers, on the other hand, often require user licenses for each website hosted on the the server.

Linux is available in several distributions. Some of the most popular distributions include Red Hat Enterprise, CentOS, Debian, openSUSE, and Ubuntu. Linux also supports several hardware platforms, including Intel, PowerPC, DEC Alpha, Sun Sparc, and Motorola. Since Linux is compatible with so many types of hardware, variations of the Linux operating system are used for several other electronic devices besides computers. Some examples include cell phones, cable boxes, and Sony's PS2 and PS3 gaming consoles.

Mac OS Definition

This is the operating system that runs on Macintosh computers. It is pronounced, "mack-oh-es." The Mac OS has been around since the first Macintosh was introduced in 1984. Since then, it has been continually updated and many new features have been added to it. Each major OS release is signified by a new number (i.e. Mac OS 8, Mac OS 9).

Since the core of the Mac OS was nearly decades old, Apple decided to completely revamp the operating system. In March of 2001, Apple introduced a completely new version of the Mac OS that was written from the ground up. The company dubbed it "Mac OS X," correctly pronounced "Mac OS 10." Unlike earlier versions of the Mac OS, Mac OS X is based on the same kernel as Unix and has many advanced administrative features and utilities. Though the operating system is much more advanced than earlier versions of the Mac OS, it still has the same ease-of-use that people have come to expect from Apple software.