Computer Basics 
Understanding Operating Systems
What is an operating system?
An 
operating system is the 
most important software that runs on a computer. It manages the computer's 
memory, 
processes, and all of its 
software and 
hardware. It also allows you to 
communicate with the computer without knowing how to speak the computer's language. 
Without an operating system, a computer is useless.
The operating system's job
Your computer's 
operating system (
OS) manages all of the
 software and
 hardware on
 the computer. Most of the time, there are many different computer 
programs running at the same time, and they all need to access your 
computer's 
central processing unit (CPU), 
memory, and 
storage. The operating system coordinates all of this to make sure each program gets what it needs.
Types of operating systems
Operating systems usually come 
preloaded on any 
computer you buy. Most people use the operating system that comes with 
their computer, but it's possible to upgrade or even change operating 
systems.
The three most common operating systems for personal computers are Microsoft Windows, Apple Mac OS X, and Linux.
Modern operating systems use a 
graphical user interface, or 
GUI (pronounced 
gooey). A GUI lets you use your mouse to click 
icons, 
buttons, and 
menus, and everything is clearly displayed on the screen using a combination of 
graphics and 
text.
 
Each operating system's GUI has a different look and feel, so if you 
switch to a different operating system it may seem unfamiliar at first. 
However, modern operating systems are designed to be 
easy to use, and most of the basic principles are the same.
 
 
Microsoft Windows
Microsoft created the 
Windows operating system in 
the mid-1980s. Over the years, there have been many different versions 
of Windows, but the most recent ones are 
Windows 8 (released in 2012), 
Windows 7 (2009), and 
Windows Vista (2007). Windows comes 
preloaded on most new PCs, which helps to make it the 
most popular operating system in the world.
If you're buying a new computer or are upgrading to a newer version of Windows, you can choose from several different 
editions of Windows, such as 
Home Premium, 
Professional, and 
Ultimate. You may need to do some research to decide which edition is right for you.
 
 
Mac OS X
Mac OS is a line of operating systems created by 
Apple. It comes preloaded on all new Macintosh computers, or Macs. All 
of the recent versions are known as
 OS X (pronounced O-S Ten), and the specific versions include 
Yosemite (released in 2014), 
Mavericks (2013), 
Mountain Lion (2012), 
Lion (2011), and 
Snow Leopard (2009). Apple also offers a version called 
Mac OS X Server, which is designed to be run on servers.
According to 
StatCounter Global Stats, Mac OS X users account for 
9.5% of the operating systems market as of September 2014—much lower than the percentage of Windows users (almost 
90%).
 One reason for this is that Apple computers tend to be more expensive. 
However, many people prefer the look and feel of Mac OS X.
 
 
Linux
Linux (pronounced 
LINN-ux) is a family of 
open-source operating systems, which means they can be modified and distributed by anyone around the world. This is different from 
proprietary software like Windows, which can only be modified by the company that owns it (Microsoft). The advantages of Linux are that it is 
free, and there are many different 
distributions—or versions—you can choose from. Each distribution has a different look and feel, and the most popular ones include 
Ubuntu, 
Mint, and 
Fedora.
Linux is named after Linus Torvalds, who created the Linux kernel in 1991. The kernel is the computer code that is the central part of an operating system.
According to 
StatCounter Global Stats, Linux users account for less than 
2% of the operating systems market as of September 2014. However, most 
servers run Linux because it's relatively easy to customize.
 
 
Operating systems for mobile devices
The operating systems we've been talking about were designed to run on 
desktop or 
laptop computers. 
Mobile devices such as 
phones, 
tablet computers, and 
MP3 players
 are different from desktop and laptop computers, so they run operating 
systems that are designed specifically for mobile devices. Examples of 
mobile operating systems include 
Apple iOS, 
Windows Phone, and 
Google Android. In the screenshot below, you can see Apple iOS running on an iPad.
Operating systems for mobile devices generally aren't as fully 
featured as those made for desktop and laptop computers, and they aren't
 able to run all of the same software. However, you can still do a lot 
of things with them, like watch movies, browse the Web, manage your 
calendar, and play games.
