A computer is an electronic machine that can perform mathematical calculations and logical comparisons quickly without errors. It takes in data as input, processes it according to instructions, and provides results as output or stores them. Computers consist of hardware, the physical components, and software which provides instructions to the hardware. When a computer is turned on, a program called the BIOS loads the operating system from permanent storage like a hard disk into temporary memory (RAM) to control the hardware. The CPU then processes data from input devices according to the operating system, and sends results to output devices like monitors or saves them to permanent storage. Main types of computers are mainframes for large organizations, minicomputers formerly for mid-sized businesses, super

1. What is a Computer?

2. What is a Computer?
• 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. They can store
the results forever.

3. What is a Computer?
• 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. How do computers work?
Booting Up Your Computer
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). This
process is known as booting, or booting
up, which is short for bootstrapping.

5. How do computers work?
Booting Up Your Computer
• 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 last as long as the
computer is switched on.

6. How do computers work?
Data Flow in a Computer
• When you switch on a computer, first, a special software
called the operating system is copied (loaded) from
permanent storage to the RAM. The computer gets data
from an input device, such as a keyboard, mouse, hard disk,
or scanner, and makes all the calculations and the
comparisons in the central processing unit (CPU).

7. How do computers work?
Data Flow in a Computer
• 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.

8. Data Flow in a Computer

10. TYPES OF COMPUTERS
• 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, using either a Personal
Computer (PC) or a Dumb
Terminal. A PC performs a lot of
processing itself. A dumb terminal
uses the mainframe computer to
do all the processing and just
shows the results on a screen.
Large organizations, for example,
banks and insurance companies,
use mainframe computers.

11. TYPES OF COMPUTERS
• Minicomputers
Like mainframe computers, minicomputers
are multi-user computers. They are very
powerful and expensive. Mainframes and
minicomputers are used for very similar
purposes. Middle-sized companies use
minicomputers.
As microcomputers developed in 1970s
and 1980s, minicomputers filled the mid-
range area between low powered single-
user microcomputers and high capacity
multi-user mainframes. Since
microcomputers have become more
powerful and the PC networks emerged in
1980s and 1990s, the minicomputers role
has been filled by microcomputers.

12. TYPES OF COMPUTERS
• Supercomputers
A supercomputer is a mainframe computer that is incredibly
powerful and has a very large capacity for processing data.
Supercomputers are often used by the military services. They are
also used for such research as weather forecasting, in which a huge
amount of data must be processed rapidly.

13. TYPES OF COMPUTERS
• 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.

14. Questions