1. What is a Computer?

2. A computer is an electronic machine that makes mathematical calculations and logical comparisons quickly and without any mistakes.
Computers take data, process them according to a list of instructions, and show or store the results of the processing.

3. Computers consist of two parts, hardware and software.
Hardware is the physical parts of the computer. Software is the programs in the computer.
Software tells the hardware what to do. The relation between hardware and software is like the relation between our body and our mind.

4. What is a Computer?

5. HOW COMPUTERS WORK
When you switch on your computer, a small initiating program BIOS (Basic Input/Output System or Built In Operating System) is loaded into memory (RAM).
The BIOS software is written in a ROM on the mainboard. The primary function of the BIOS is to identify and initialize system hardware devices and to copy (load) the operating system software from permanent storage to RAM (Random Access Memory).

6. HOW COMPUTERS WORK
This process is known as booting, or booting up, which is short for bootstrapping.
ROM (Read-Only Memory) can be read but not changed. It contains the basic information needed to start the computer. A long life battery in the computer sustains the memory when the computer is turned off. Data are placed in ROM only once and stay there permanently.

7. The mainboard is the central board in the computer that all devices are connected to

8. HOW COMPUTERS WORK
Computers can store information in two different ways: in permanent storage (for example, on a disk or a CD) and in temporary storage, also called the computer’s memory or RAM. Data in temporary storage only survives as long as the computer is switched on.
When you switch on a computer; first, a special software called the operating system is loaded from permanent storage to the RAM.

9. HOW COMPUTERS WORK
The computer gets data from an input device, such as a keyboard, mouse, or scanner, and performs all the calculations and/or the comparisons in the central processing unit (CPU).
The CPU is like the computer’s brain. It uses the RAM to maintain the data.
When the CPU has processed the data, it sends the results to an output device, such as a monitor or printer, or saves them in a permanent storage device, such as a hard disk.

10. Operating System
An Operating System is a master program that controls a computer’s basic functions and allows other programs to access the computer’s resources, such as disk drive, printer, keyboard, and screen.
It provides the interface between a human and a computer. Microsoft Windows 8 and Linux are two examples of operating systems.

12. Activity

13. Activity

14. TYPES OF COMPUTERS

15. Mainframe Computers
A mainframe computer is a big, powerful, and expensive computer. Many people can use the power of a mainframe computer at the same time,
They are used in banking, airlines and railways etc.. for their applications.

16. Mini Computers
Like mainframe computers, minicomputers are multi-user computers. Mini computers are lower to mainframe computers in terms of speed and storage capacity.
They are also less expensive than mainframe computers. Some of the features of mainframes are not available in mini computers.

17. Supercomputers
A supercomputer is a mainframe computer that is incredibly powerful and has a very large capacity for processing data.
A supercomputer is a computer at the frontline of contemporary processing capacity
Supercomputers are often used by the military services and space exploration. They are also used for such research as weather forecasting, in which a huge amount of data must be processed rapidly.

18. Supercomputers
Cray-2 was the world’s fastest computer in the 1980s. It was used by U.S. Departments of Defense and Energy for nuclear weapons research, by NASA’s Ames Research Center and by universities and corporations worldwide for different purposes.

19. Supercomputers
IBM Sequoia, IBM Roadrunner, IBM Blue Gene, and NEC Earth Simulator are the world’s fastest computers.
Tianhe-2 or TH-2 is a petaflops supercomputer located in Sun Yat-sen University, Guangzhou, China. It was developed by a team of 1,300 scientists and engineers.

20. Microcomputers
Microcomputers are usually used only by one person at a time. An IBM PC and Apple Macintosh are two kinds of microcomputers.
There are desktop, laptop, palmtop, tabletop, pocket, tablet, and netbook models of microcomputers.

21. Review Questions What’s a computer? Explain how a computer boots.
Which storing ways are available for a computer?
What’s an operating system?
What types of computers are there? Explain all types.