What is Computer?

Definition no: 1 A computer generally means a programmable machine. The two principal characteristics of a computer are: it responds to a specific set of instructions in a well-defined manner and it can execute a prerecorded list of instructions (a program)

Definition no: 2A computer is a device that accepts information (in the form of digitalized data) and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed.

Definition no: 3Computer is also called processor. An electronic device designed to accept data, perform prescribed mathematical and logical operations at high speed, and display the results of these operations.

Definition no: 4An electronic device which is capable of receiving information (data) in a particular form and of performing a sequence of operations in accordance with a predetermined but variable set of procedural instructions (program) to produce a result in the form of information or signals.

Definition no: 5General purpose machine, commonly consisting of digital circuitry, that accepts (inputs), stores, manipulates, and generates (outputs) data as numbers, text, graphics, voice, video files, or electrical signals, in accordance with instructions called a program.

Types of ComputerSince the advent of the first computer different types and sizes of computers are offering different services. Computers can be as big as occupying a large building and as small as a laptop or a microcontroller in mobile & embedded systems. The four basic types of computers are.

1. Super computer2. Mainframe Computer

3. Minicomputer

4. Microcomputer

1. Super ComputerThe most powerful computers in terms of performance and data processing are the supercomputers. These are specialized and task specific computers used by large organizations. These computers are used for research and exploration purposes, like NASA uses supercomputers for launching space shuttles, controlling them and for space exploration purpose.The supercomputers are very expensive and very large in size. It can be accommodated in large air-conditioned rooms; some super computers can span an entire building.

Uses of SupercomputerIn Pakistan and other countries Supercomputers are used by Educational Institutes like NUST (Pakistan) for research purposes. Pakistan Atomic Energy commission & Heavy Industry Taxila uses supercomputers for Research purposes.

Space Exploration Supercomputers are used to study the origin of the universe, the dark-matters. For these studies scientist use IBM’s powerful supercomputer “Roadrunner” at National Laboratory Los Alamos.

Earthquake studies Supercomputers are used to study the Earthquakes phenomenon. Besides that supercomputers are used for natural resources exploration, like natural gas, petroleum, coal, etc.

Weather Forecasting Supercomputers are used for weather forecasting, and to study the nature and extent of Hurricanes, Rainfalls, windstorms, etc.

Nuclear weapons testing Supercomputers are used to run weapon simulation that can test the Range, accuracy & impact of Nuclear weapons.   

Popular Supercomputersa.  IBM’s Sequoia, in United Statesb.  Fujitsu’s K Computer in Japan

c.  IBM’s Mira in United States

d.  IBM’s SuperMUC in Germany

e.  NUDT Tianhe-1A in China

2. Mainframe computer

Although Mainframes are not as powerful as supercomputers, but certainly they are quite expensive nonetheless, and many large firms & government organizations uses Mainframes to run their business operations. The Mainframe computers can be accommodated in large air-conditioned rooms because of its size. Super-computers are the fastest computers with large data storage capacity, Mainframes can also process & store large amount of data. Banks educational institutions & insurance companies use mainframe computers to store data about their customers, students & insurance policy holders.

Popular Mainframe computersa.  Fujitsu’s ICL VMEb.  Hitachi’s Z800

3. MinicomputersMinicomputers are used by small businesses & firms. Minicomputers are also called as “Midrange Computers”. These are small machines and can be accommodated on a disk with not as processing and data storage capabilities as super-computers & Mainframes. These computers are not designed for a single user. Individual departments of a large company or organizations use Mini-computers for specific purposes. For example, a production department can use Mini-computers for monitoring certain production process.

Popular Minicomputersa.  K-202b.  Texas Instrument TI-990

c.  SDS-92

d.  IBM Midrange computers

4. MicrocomputersDesktop computers, laptops, personal digital assistant (PDA), tablets & smartphones are all types of microcomputers. The micro-computers are widely used & the fastest growing computers. These computers are the cheapest among the other three types of computers. The Micro-computers are specially designed for general usage like entertainment, education and work purposes. Well known manufacturers of Micro-computer are Dell, Apple, Samsung, Sony and Toshiba.

Types of Microcomputers

1. Personal ComputerThe personal computer (PC) defines a computer designed for general use by a single person. While a Mac is a PC, most people relate the term with systems that run the Windows operating system. PCs are known as microcomputers because they are a complete computer, built on a smaller scale than the huge systems in use by most businesses.

2. DesktopA PC that is not designed for portability is a desktop computer. The expectations with desktop systems are that you will set the computer up in a permanent location. Most desktops offer more power, storage and versatility for less cost than their portable.

3. LaptopsAlso called notebooks, laptops are portable computers that integrate the display, keyboard, a pointing device or

trackball, processor, memory and hard drive all in a battery-operated package slightly larger than an average hardcover book.

4. NetbooksNetbooks are ultra-portable computers that are even smaller than traditional laptops. The extreme cost-effectiveness of netbooks (roughly $300 to $500) means they're cheaper than almost any brand-new laptop you'll find at retail outlets. However, netbooks' internal components are less powerful than those in regular laptop.

5. Personal Digital Assistants (PDAs) PDA’s are tightly integrated computers that often use flash memory instead of a hard drive for storage. These computers usually do not have keyboards but rely on touchscreen technology for user input. PDAs are typically smaller than a paperback novel, very lightweight with a reasonable battery life. A slightly larger and heavier version of the PDA is the handheld computer.

6. WorkstationsAnother type of computer is a workstation. A workstation is simply a desktop computer that has a more powerful processor, additional memory and enhanced capabilities for performing a special group of task, such as 3D Graphics or game development.

7. Wearable computersThe latest trend in computing is wearable computers. Essentially, common computer applications (e-mail, database, multimedia, and calendar/scheduler) are integrated into watches, cell phones, and even clothing.

8. Palmtop ComputerA palmtop computer is similar to a laptop computer, but smaller. It's small enough to fit in the palm of your hand (hence the name!)Palmtops are usually not very powerful since fast CPUs require a large battery and get hot - both problems in a small device. A typical palmtop have a very

small keyboard - too small to type on normally, instead the user types using both thumbs. Also there is no room for a track pad, so a touchscreen or tiny joystick is used instead. Palmtops are extremely portable, but the small keyboard and screen make the devices tiring to use for long periods.

9. Tablet PCA tablet, or tablet PC, is a portable computer that uses a touchscreen as its primary input device. Most tablets are slightly smaller and weigh less than the average laptop. While some tablets include fold out keyboards, others, only offer touchscreen input.Early tablet touchscreens were designed to work with light pens, but most modern tablets support human touch input. Many tablets now support multi-touch input, which allows you to perform gestures with multiple fingers, such as pinching an image to zoom out, or spreading your fingers apart to zoom in. Tablets without physical keyboards allow you to enter text using a pop-up keyboard that appears on the screen.Since tablet PCs provide a different interface than traditional computers, they offer unique possibilities for graphics applications, games, and other programs. Because of their small form factor, they are extremely portable and can be easily stored in a backpack or a briefcase. Still, because tablets lack a keyboard and mouse, some tasks such as typing documents and writing email messages, are more difficult on tablets than traditional computers. Therefore, tablets are generally seen as accessories to laptops and desktop computers rather than replacements.