What is a Computer?

A computer is an electronic device that manipulates information, or "data." It has the ability to store, retrieve, and process data.
 You can use a computer to type documents, send email, and browse the internet. You can also use it to handle spreadsheets, accounting, database management, presentations, games, and more.

Basic Parts of Computer

Basically there are three parts of computer-

1. C.P.U (Central Processing Unit)-

            It is the hardware within the computer that carries out the instructions of computer program by  performing basic arithmetical, logical, and input output operations of the system.

 CPU(central processing unit) is generally compared with the human brain,which is 100% correct.

 It works in same manner as that of brain. The only problem with it is only that it can't think himself. 

    2.  Keyboard-e

           Keyboard is a device consisting set of buttons or keys having alphabets, numbers, symbols, etc. printed on them which on pressing them give input/instructions to C.P.U to work/process as desired.

          Normally it consists of 103 keys/buttons. (Keys may vary with manufacturer).

   3. Computer screen(Monitor)-

      

             It is an output device that display information, pictures, videos, etc. that is processed in C.P.U according to the information provided by user.

C.P.U (Central Processing Unit)

C.P.U consists of -

  1.  Processor-
       
             Every part has some purpose to run the computer. processor is the main part of CPU. all are saying that Processor is the heart of computer or brain of computer compared with the human. processor is process or execute the data what you have given. heat will generate automatically, so to control the processor heat there is a fan, this is called processor heatsink and fan.

  2.  Mother Board-
     
               After processor, motherboard is the main part because all remaining parts are connected to motherboard only. motherboard is a main circuit board, which has socket, ram slots, other slots and ports to connect. 


  3. RAM-

             
                RAM full form is Random Access Memory. which is primary memory and temporary storaging device. 


  4. Hard Disk Drive-

                Hard disk drive is a main storaging device, it is a secondary memory.

  5. CD/DVD-

               These drives are used to read and write the CD or DVDs.

  6. SMPS-

               SMPS full form is Switching Mode Power Supply. which is main power supply to power all the parts of CPU
  

Monitor

There are two basic types of monitors:
                      
             CRT (cathode ray tube) monitors and LCD (liquid crystal display) monitors. Both types produce sharp images, but LCD monitors have the advantage of being much thinner and lighter. CRT monitors, however, are generally more affordable.

Keyboard

• The function keys, found on the top row, perform different functions depending on where they are used.
• The numeric keypad, located on the right side of most keyboards, allows you to enter numbers quickly.
• The navigation keys, such as the arrow keys, allow you to move your position within a document or webpage.

Other Important Parts of Computer

1. Mouse-

           A mouse is a small device used to point to and select items on your computer screen. Although mice come in many shapes, the typical mouse does look a bit like an actual mouse. It's small, oblong, and connected to the system unit by a long wire that resembles a tail. Some newer mice are wireless.


2. Speakers-

         Speakers are used to play sound. They may be built into the system unit or connected with cables. Speakers allow you to listen to music and hear sound effects from your computer.


3. Modem-

        To connect your computer to the Internet, you need a modem. A modem is a device that sends and receives computer information over a telephone line or high-speed cable. Modems are sometimes built into the system unit, but higher-speed modems are usually separate components.


4. Printers-
    
       A printer transfers data from a computer onto paper. You don't need a printer to use your computer, but having one allows you to print e‑mail, cards, invitations, announcements, and other materials. Many people also like being able to print their own photos at home.

The two main types of printers are inkjet printers and laser printers. Inkjet printers are the most popular printers for the home. They can print in black and white or in full color and can produce high-quality photographs when used with special paper. Laser printers are faster and generally better able to handle heavy use.

Types of Computers

1. Desktop Computers-

            Desktop computers are designed for use at a desk or table. They are typically larger and more powerful than other types of personal computers. Desktop computers are made up of separate components. The main component, called the system unit, is usually a rectangular case that sits on or underneath a desk. Other components, such as the monitor, mouse, and keyboard, connect to the system unit.

2. Laptop Computers-

           Laptop computers are lightweight mobile PCs with a thin screen. They are often called notebook computers because of their small size. Laptops can operate on batteries, so you can take them anywhere. Unlike desktops, laptops combine the CPU, screen, and keyboard in a single case. The screen folds down onto the keyboard when not in use.



3.Handheld Computers-

         Handheld computers, also called personal digital assistants (PDAs), are battery-powered computers small enough to carry almost anywhere. Although not as powerful as desktops or laptops, handhelds are useful for scheduling appointments, storing addresses and phone numbers, and playing games. Some have more advanced capabilities, such as making telephone calls or accessing the Internet. Instead of keyboards, handhelds have touch screens that you use with your finger or a stylus (a pen-shaped pointing tool).

4.Tablet PC's-

       Tablet PCs are mobile PCs that combine features of laptops and handhelds. Like laptops, they're powerful and have a built-in screen. Like handhelds, they allow you to write notes or draw pictures on the screen, usually with a tablet pen instead of a stylus. They can also convert your handwriting into typed text. Some Tablet PCs are “convertibles” with a screen that swivels and unfolds to reveal a keyboard underneath.

Super Computers

The fastest type of computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations. For example, weather forecasting requires a supercomputer. Other uses of supercomputers include animated graphics, fluid dynamic calculations, nuclear energy research, and petroleum exploration.

The chief difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible, whereas a mainframe uses its power to execute many programs concurrently.

Operating System (OS)

An operating system (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs. The operating system is an essential component of the system software in a computer system. Application programs usually require an operating system to function.

Time-sharing operating systems, schedule tasks for efficient use of the system and may also include accounting for cost allocation of processor time, mass storage, printing, and other resources.
For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and will frequently make a system call to an OS function or be interrupted by it. Operating systems can be found on almost any device that contains a computer—from cellular phones and video game consoles to supercomputers and web servers.

Examples of Operating System

1. Android
2. BSD
3.  iOS
4.  GNU/Linux
5.  OS X
6.  QNX
7. Microsoft Windows
8. Windows Phone
9. IBM z/OS.

Types of operating systems

1.Real-time-

            A real-time operating system is a multitasking operating system that aims at executing real-time applications. Real-time operating systems often use specialized scheduling algorithms so that they can achieve a deterministic nature of behavior. The main objective of real-time operating systems is their quick and predictable response to events. They have an event-driven or time-sharing design and often aspects of both. An event-driven system switches between tasks based on their priorities or external events while time-sharing operating systems switch tasks based on clock interrupts.

 2.Multi-user-

           A multi-user operating system allows multiple users to access a computer system at the same time. Time-sharing systems and Internet servers can be classified as multi-user systems as they enable multiple-user access to a computer through the sharing of time. Single-user operating systems have only one user but may allow multiple programs to run at the same time.

 3.Multi-tasking vs. single-tasking-

          A multi-tasking operating system allows more than one program to be running at the same time, from the point of view of human time scales. A single-tasking system has only one running program. Multi-tasking can be of two types: pre-emptive and co-operative. In pre-emptive multitasking, the operating system slices the CPU time and dedicates one slot to each of the programs. Unix-like operating systems such as Solaris and Linux support pre-emptive multitasking, as does AmigaOS. Cooperative multitasking is achieved by relying on each process to give time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking. 32-bit versions of both Windows NT and Win9x, used pre-emptive multi-tasking. Mac OS prior to OS X used to support cooperative multitasking.

4.Distributed-

         Further information: Distributed system
A distributed operating system manages a group of independent computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing. Distributed computations are carried out on more than one machine. When computers in a group work in cooperation, they make a distributed system.

5.Embedded

            Embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy. They are able to operate with a limited number of resources. They are very compact and extremely efficient by design. Windows CE and Minix 3 are some examples of embedded operating systems