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Operating Systems Tutorial


Your computer can have an expensive motherboard, the fastest processor, lots of memory, and superior graphics, but it is completely useless without an operating system (OS). Every computer must have one. What is the operating system? You can look at it as being the "middle man". Application software such as a spreadsheet cannot communicate directly with hardware. Whether pressing a key on your keyboard or clicking your mouse, it's the computer operating system that provides the interface between software and hardware. It handles all of the computer's resources and has the ability to support devices from many different vendors via device drivers. All these tasks are quietly working behind the scenes without the user's knowledge.

Types of Operating Systems:
There are four types of computer operating systems: A Real Time OS is for industry and machines. There's basically no user involvement. A single-user single task operating system is for one person to do one thing at a time. A single-user multitask OS allows one person to run more than one application on a computer simultaneously. A multi-user operating system permits multiple users to access a single computer.

Other Basics:
Whether it's Windows, Mac, or Linux, operating systems have a Kernel. The Kernel is the heart of an operating system, the part that does the invisible work such as allowing user applications access to hardware, managing resources like the memory and CPU, scheduling tasks, and storing device drivers. It is usually the first part of the OS that is loaded after you turn on your computer and it completes the POST (Power On Self Test). If a problem occurs at any point when the OS is loading, usually an error message appears on the screen.

Since Windows ME, the Windows family has been based on the WinNT architecture. The first version was NT 3.1, and there were other versions in the 3.x group which was followed by NT 4.0. Linux and Mac are based on Unix. Both the Windows and Linux/Mac architecures consist of a layered structure with User mode sitting on top of the Kernel. In order to make user applications work it takes an API (Application Program Interface) & libraries. An API consists of pre-made tools that aid in writing software. A library is a collection of often used functions or other code that can be implemented by various programs. That way, a programmer doesn't have to rewrite the same code every time it's needed. Windows uses Dynamic Link Libraries, which simply means the library is called during run time, i.e. when a program is actually running. Another way of looking at it is the library is used only when needed. Dynamic Link Libraries usually have a .dll extension.

The Registry:
The computer registry is where all system settings are stored. Whether personal settings or those from an installed application, everything is placed in the registry. Anytime a change is made to your system, the registry is updated to reflect that change. The settings are stored in files, but these files cannot be opened and edited directly. In order to access them you have to open the Registry Editor. From there you can view and make changes.

The registry contains a left and right pane, and everything is arranged in a hierarchy, like Windows Explorer. It consists of three components: keys, subkeys, and values. Collectively these are called hives. The keys are the main categories and are located in the left pane. Below the keys are the subkeys, which may contain more subkeys. When you click on a subkey, the value appears on the right side. Let's take a look.To open Registry Editor in Windows XP click Start, Run, & type regedit. To open in Vista click start, then type regedit in the "Start Search" text box. It automatically begins to look for the program. After found, it should appear in the area above the text box. Double click the icon.

When the windows appears, notice the main key categories on the left. Each stores certain settings.

Computer Registry
  • HKEY_CLASSES_ROOT (HKCR): Deals with settings such as shortcuts and file associations.
  • HKEY_CURRENT_USER (HKCU): Stores data for the current person who's logged in. These will change depending on who is using the computer.
  • HKEY_LOCAL_MACHINE (HKLM): Contains the settings about a computer's hardware and software configuration.
  • HKEY_USERS (HKU): Stores information about all users that are logged in.
  • HKEY_CURRENT_CONFIG (HKCC): Stores hardware information used by the computer at startup.
Double clicking one of the keys will reveal subkeys beneath the main key. Clicking on a subkey will display its value(s) in the right pane. In this example the key HKEY_LOCAL_MACHINE and the Components subkey are selected.

Computer Registry

To edit a value, right click the one that needs to be changed and click modify.

Computer Registry

Change the value where it says "Value data" and click OK.

Computer Registry

Manually editing the computer registry is very dangerous if you don't know what you're doing. Making the wrong change can screw up your system. Even if you use a registry cleaning application, you still need to be sure the correct entries are being deleted. If you have any doubts, don't do it. As far as changing values, it's very rare if you will have to do so, but make sure you backup your registry before making any changes.







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