Yonas Tibebu

The Internet is the most commonly and widely used computer network, but it isn't the only type of computer network for sharing information digitally. The Internet, an intranet and an extranet are three similar, but distinct types of networks. While the Internet is open to anyone and everyone, intranets and extranets are designed for smaller groups of people. Think of the latter two as larger versions of a personal home network. Internet The Internet is a network that is available to anyone with an Internet-connected device. It is a massive collection of networks sharing information publicly in the form of interlinked Web pages. Internet Protocol defines a site's unique location which most users see as a domain name or URL. The network is literally world-wide and is often referred to as the world wide web. Intranet An intranet network is only available to a small group of people. Intranets are mainly used within businesses and organizations to provide access to files...

The heart of managing the processor comes down to two related issues: ·          Ensuring that each process and application receives enough of the processor's time to function properly ·          Using as many processor cycles as possible for real work The basic unit of software that the operating system deals with in scheduling the work done by the processor  is either a  process  or a  thread , depending on the operating system. It's tempting to think of a process as an application, but that gives an incomplete picture of how processes relate to the operating system and hardware. The application you see (word processor, spreadsheet or game) is, indeed, a process, but that application may cause several other processes to begin, for tasks like communications with other devices or other computers. There are also numerous processes that run without giving you direct evidence that ...

When you turn on the power to a computer, the first program that runs is usually a set of instructions kept in the computer's  read-only memory  (ROM). This code examines the system hardware to make sure everything is functioning properly. This  power-on self-test  (POST) checks the CPU,  memory , and  basic input-output systems  (BIOS) for errors and stores the result in a special memory location. Once the POST has successfully completed, the software loaded in ROM (sometimes called the BIOS or firmware ) will begin to activate the computer's disk drives. In most modern computers, when the computer activates the  hard disk drive, it finds the first piece of the operating system: the  bootstrap loader . The bootstrap loader is a small program that has a single function: It loads the operating system into memory and allows it to begin operation. In the most basic form, the bootstrap loader sets up the small driver programs that interface ...

Within the broad family of operating systems, there are generally four types, categorized based on the types of computers they control and the sort of applications they support. The categories are: ·          Real-time operating system (RTOS) - Real-time operating systems are used to control machinery, scientific instruments and industrial systems. An RTOS typically has very little user-interface capability, and no end-user utilities, since the system will be a "sealed box" when delivered for use. A very important part of an RTOS is managing the resources of the computer so that a particular operation executes in precisely the same amount of time, every time it occurs. In a complex machine, having a part move more quickly just because system resources are available may be just as catastrophic as having it not move at all because the system is busy. ·          Single-user, single task  - As the na...

At the simplest level, an operating system does two things: 1.      It manages the hardware and software resources of the system. In a  desktop computer , these resources include such things as the processor ,  memory , disk space and more (On a  cell phone , they include the keypad, the screen, the address book, the phone dialer, the battery and the network connection). 2.      It provides a stable, consistent way for applications to deal with the hardware without having to know all the details of the hardware. The first task, managing the hardware and software resources, is very important, as various programs and input methods compete for the attention of the  central processing unit  (CPU) and demand memory, storage and input/output (I/O) bandwidth for their own purposes. In this capacity, the operating system plays the role of the good parent, making sure that each application gets the necessary resources wh...

Not all computers have operating systems. The computer that controls the  microwave oven  in your kitchen, for example, doesn't need an operating system. It has one set of tasks to perform, very straightforward input to expect (a numbered keypad and a few pre-set buttons) and simple, never-changing hardware to control. For a computer like this, an operating system would be unnecessary baggage, driving up the development and manufacturing costs significantly and adding complexity where none is required. Instead, the computer in a microwave oven simply runs a single hard-wired program all the time. For other devices, an operating system creates the ability to: ·          serve a variety of purposes ·          interact with users in more complicated ways ·          keep up with needs that change over time All desktop computers have operating systems....

When you turn on your   computer, it's nice to think that you're in control. There's the trusty computer   mouse, which you can move anywhere on the screen, summoning up your music library or   Internet   browser at the slightest whim. Although it's easy to feel like a director in front of your desktop or   laptop, there's a lot going on inside, and the real man behind the curtain handling the necessary tasks is the operating system. Most desktop or laptop PCs come pre-loaded with Microsoft Windows. Macintosh computers come pre-loaded with Mac OS X. Many corporate servers use the Linux or UNIX operating systems. The operating system (OS) is the first thing loaded onto the computer -- without the operating system, a computer is useless. More recently, operating systems have started to pop up in smaller computers as well. If you like to tinker with electronic devices, you're probably pleased that operating systems can now be found on many of the devices we u...

uses our current knowledge of physics to develop a cryptosystem that is not able to be defeated - that is, one that is completely secure against being compromised without knowledge of the sender or the receiver of the messages. The word  quantum  itself refers to the most fundamental behavior of the smallest particles of matter and energy: quantum theory explains everything that exists and nothing can be in violation of it. Quantum cryptography is different from traditional cryptographic systems in that it relies more on physics, rather than mathematics, as a key aspect of its security model. Essentially, quantum cryptography is based on the usage of individual particles/waves of light (photon) and their intrinsic quantum properties to develop an unbreakable cryptosystem - essentially because it is impossible to measure the quantum state of any system without disturbing that system. It is theoretically possible that other particles could be used, but photons offer all t...