Operating System

What is an Operating System?
An operating system is a program that acts as an intermediary between the user of a computer and the computer hardware. It is an important part of almost every computer system. It is the most important program that runs on a computer. Every general-purpose computer must have an operating system to run other programs. It also provides a basis for application programs.
The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner. An operating system is a program that manages the computer hardware. Operating systems perform basic tasks, such as recognizing input from the keyboard, sending output to the display screen, keeping track of files and directories on the disk, and controlling peripheral devices such as disk drives and printers.

How Operating System Works?

For a computer to start running—for instance, when it is powered up or rebooted — it needs to have an initial program to run. This initial program or Bootstrap program, tends to be simple. Typically, it is stored in Read-Only Memory (ROM) such as EEPROM within the computer hardware.
Booting Process
Because operating systems take up so much memory, they must be stored on your hard drive until they can be loaded into random access memory (RAM). The Bootstrap program must know how to load the operating system and to start executing that system. When you turn on your computer, your PC’s BIOS (Basic Input Output System) places a small amount of operating system code into RAM. As a result, the reminder of the operating system is loaded into memory. The operating system then starts executing the first process, such as “init”, and waits for some event to occur.
KERNEL
The kernel is the part of the operating system that deals with your hardware. As the user, you never work with the kernel itself. You must interact with it through a shell program.
SHELL
The shell program is the visual setting you see when you use your computer. It is also the part of the operating system where users can issue commands to the computer. Some operating systems use a command line interface that allows you to type in specific commands. Others have a graphical user interface (GUI). GUIs use windows, menus, and icons to help you control your computer. Some operating systems have a variety of GUIs, allowing users to select the one they want.

Examples of Operating System

1. Microsoft Windows

Microsoft Windows is a family of proprietary operating systems that originated as an add-on to the older MS-DOS operating system for the IBM PC. Modern versions are based on the newer Windows NT kernel that was originally intended for OS/2. Windows runs on x86, x86-64 and Itanium processors. Earlier versions also ran on the Alpha, MIPS, Fairchild (later Intergraph) Clipper and PowerPC architectures (some work was done to port it to the SPARC architecture).

If you got this one right then congratulations you most likely have a pulse and a few brain cells. Any version of windows counts by the way so if you said DOS (I know, it’s not really Windows but most people don’t make the distinction), 3.1, 9x, Me (shudder), NT, 2000, XP or Vista you get a point. If you didn’t guess Windows then you probably have never scene a computer and thus must be quite mystified that you can read glowing letters on a magic box. Be careful, because as you are reading this last sentence I am stealing your soul and putting it in a little shiny mirror. Oh, too late, you finished reading and I now have your soul. That is what you get for looking at magic glowing boxes. Now be gone before I try and convince you to buy some water front property from a Nigerian banker who made all of his money helping orphans while selling male growth hormones so he could get his college degree online with 0% financing.
2. Macintosh

Mac OS X is a line of computer operating systems developed, marketed, and sold by Apple Inc., and since 2002 has been included with all new Macintosh computer systems. It is the successor to Mac OS 9, the final release of the "classic" Mac OS, which had been Apple's primary operating system since 1984.

Well, you are reading this on a site called Apple Matters so I would be kind of worried if you missed this one. So, give yourself another point if you guessed Mac OS Classic, System 7-9.2, OS X or if you said Lisa. Actually, if you said Lisa give yourself a pat on the back and congratulate yourself for knowing your Apple history. If you missed this one chances are good that you are not too adept at using computers. Also you might have also missed the iPod craze as well.
3. Palm

I almost didn’t count this one but decided at the last minute to let it squeak by. If you have ever used a PDA before chances are good you have seen a Palm Pilot. You probably have even played with one in the store. And maybe you even still have one in a desk drawer somewhere. If so, go dig it out, dust it off and put it on eBay. And while you are at it give yourself a point.
4. Linux

If you said Linux or could name any of the distros then you are either a geek or related to one. Redhat, Ubuntu, Knoppix, Slackware, Debian all count and deserve one point. If you just said Linux then you still get the point on a technicality.
5. UNIX

Solaris counts. So does AIX, the BSDs or any other Unix variant you can name. So give yourself a point for remembering one of the oldest and most stable operating systems ever made.
6. BeOS/ZETA

If you know your Apple history then you will remember that an ex-Apple employee created the Be Operating System and latter hoped to sell it back to Apple so it could serve as the core of their next generation OS. However BeOS would ultimately not be chosen and, after a few years of languishing, eventually die. However in recent times it has been resurrected, born anew as ZETA. You are quite the technophile if you guessed either of these so give yourself a point as you marvel at the depth of your tech knowledge.
7. NextStep

After leaving Apple Steve Jobs went on to found NEXT, a company that sold its own hardware (Black Box) and its own OS (NextStep). If you are up to date on your Apple history then you already know that when Jobs returned he brought NextStep with him and that it eventually morphed into OS X. Chalk up another point for remembering Steve’s other other other company.
8. OS/2 Warp/eComStation

IBM created OS/2 and hoped that it would compete effectively against Windows. It did not. Racked with many flaws it still has managed to survive in some businesses though it never made its way onto the consumer desktop. Like BeOS it has been revitalized these last few years and given the new name of eComStation. If you remember the old name or the new give yourself a point.
9. Sendla
Now we are getting to the obscure operating systems. If you have ever heard of Sendla then chances are in the top 1% of news-reading geeks and readily deserve your point. If you are one of the 9 people who actually use Sendla then you get two points along with my condolences.
10. Amiga
If you are over 35 and have an attic you might find an Amiga in there if you look closely. If you do find one then please recycle it and use the nickel you get back to buy a piece of gum. Other uses for these machines include door stops, boat anchors and shot gun targets.
11. Plan 9
Ken Thompson, Dennis Ritchie and Douglas McIlroy at Bell Labs designed and developed the C programming language to build the operating system Unix. Programmers at Bell Labs went on to develop Plan 9 and Inferno, which were engineered for modern distributed environments. Plan 9 was designed from the start to be a networked operating system, and had graphics built-in, unlike Unix, which added these features to the design later. Plan 9 has yet to become as popular as Unix derivatives, but it has an expanding community of developers. It is currently released under the Lucent Public License. Inferno was sold to Vita Nuova Holdings and has been released under a GPL/MIT license.