HandOut#06

❖ Computer/Computer System:
A computer system is an electronic device, operating under the control of software, that can
accept data (input), manipulate data (process), and produce information (output).
Generally, the term is used to describe a collection of devices that function together as a system.

❖ Types of Computers:
There are four types of Computer:
• Microcomputer
• Minicomputer
• Mainframe computer
• Supercomputer

• Microcomputer
Can be classified into:
◼ Desktop PCs
▪ sits on desks, rarely moved, large and bulky.
▪ Memory capacity, graphics capacity and software availability vary from
one computer to another used both for business and home applications

◼ Portable PCs
▪ Can be moved easily from place to place
▪ Weight may varies
▪ Small PCs are popular known as laptop
▪ Widely used by students, scientist, reporters, etc

➢ Advantages
▪ Small size
▪ Low cost
▪ Portability
▪ Low Computing Power
▪ Commonly used for personal applications
➢ Disadvantages
▪ Low processing speed
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• Minicomputer
▪ Medium sized computer
▪ Also called the minis e.g. IBM36, HP9000, etc
▪ Computing power lies between microcomputer and mainframe computer
➢ Characteristics
▪ Bigger size than PCs
▪ Expensive than PCs
▪ Multi-User
▪ Difficult to use
▪ More computing power than PCs
▪ Used by medium sized business organizations, colleges, libraries and
banks.

➢ Advantage
▪ Cater to multiple users
▪ Lower costs than mainframes
➢ Disadvantage
▪ Large
▪ Bulky
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• Mainframe computer
▪ Known as enterprise servers
▪ Occupies entire rooms or floors
▪ Large, fast and expensive computer
▪ Cost millions of dollar

➢ Characteristics:
▪ Bigger in size than minicomputers
▪ Very expensive
▪ Support a few hundred users simultaneously (Multi-Users)
▪ Difficult to use
▪ More computing power than minicomputers
▪ Have to be kept in a special air-conditioned room
▪ Used in big business organizations and government departments

• Supercomputer
▪ Fastest and expensive
▪ Used by applications for molecular chemistry, nuclear research, weather
reports, and advanced physics
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▪ Consists of several computers that work in parallel as a single system

➢ Advantage
▪ Speed
➢ Disadvantage
▪ Generate a large amount of heat during operation

❖ Uses of Computer:
Computers in Daily Life
• Accounts
• Games
• Educational
• On-line banking
• Smart ID cards
• Supermarkets
• Working from home (Tele-working)
• Internet

❖ The Parts of a Computer System:

A complete computer system includes two distinct parts:
• Hardware
• Software
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• Hardware: Hardware is the general term that is used to describe physical artifacts of a
technology. A computer's hardware consists of electronic devices; the parts you can see and
touch.
• Software: Software is a set of electronic instructions that tells the computer how to do
certain tasks. A set of instructions is often called a program.
Software can be categorized into two types:
▪ Operating system software
▪ Application software
▪ Operating system software tells the computer system how to perform the functions of
loading, storing and executing an application and how to transfer data. Example:
Microsoft Windows: Windows XP, Windows 7, Windows 10, Apple macOS, Linux,
Android and Apple's iOS.

▪ Application Software is what USERS work with and consists of programs that tell a
computer how to produce information. Some of the more commonly used packages are:
➢ Word processing: Word Processing software is used to create and print
documents. A key advantage of word processing software is that users easily can
make changes in documents.
➢ Spreadsheet: Electronic spreadsheet software allows the user to add,
subtract, and perform user-defined calculations on rows and columns of numbers.
These numbers can be changed and the spreadsheet quickly recalculates the new
results.
➢ Database: Allows the user to enter, retrieve, and update data in an
organized and efficient manner, with flexible inquiry and reporting capabilities.
➢ Presentation graphics: Presentation graphic software allows the user to
create documents called slides to be used in making the presentations. Using special
projection devices, the slides display as they appear on the computer screen.

❖ What Does A Computer Do?

Computers can perform four general operations:
• Input
• Process
• Output
• Storage

❖ Why Is A Computer So Powerful?

• It has the ability to perform the information processing cycle with amazing speed.
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• Reliability
• Accuracy
• Ability to store huge amounts of data and information.
• Ability to communicate with other computers.

❖ The Primary Components of A Computer:

• Input devices
• Central Processing Unit CPU
• Memory
• Output devices
• Storage devices

• Input devices:
Data are facts, numbers and characters that are entered into the computer via keyboard.
Some Input devices are given below:
▪ Keyboard
▪ Mouse/Trackball
▪ Joystick
▪ Light pen
▪ Pointing Stick
▪ Touchpad
▪ Touch screen
▪ Bar code reader
▪ Scanner
▪ Microphone
▪ Graphics Tablet
▪ Digital Cameras

• Central Processing Unit (CPU):

The central processing unit (CPU) contains electronic circuits that cause processing to
occur. The CPU interprets instructions from software, performs the logical and arithmetic
processing operations, and causes the input and output operations to occur. It is
considered the “brain” of the computer.

CPU has two primary sections:

Arithmetic/logic unit: Arithmetic operations include addition, subtractions,
multiplication, and division.
- Logical operations involve comparisons.
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Control unit: is the “boss” and coordinates all of the CPU’s activities. Uses programming
instructions, it controls the flow of information through the processor by
controlling what happens inside the processor.
We communicate with the computer through programming languages.
Examples: COBOL, C++, HTML, Java Script or VisualBasic.net etc.

• Memory:
Found on the motherboard
▪ Short term
Random Access Memory (RAM)
▪ Long term
Read Only Memory (ROM)
Random Access Memory (RAM):
Memory on the motherboard that is short term; where data, information, and program
instructions are stored temporarily on a RAM chip or a set of RAM chips. Known as the main
memory. Any information stored in RAM is lost when the computer is turned off. This memory
is considered volatile. The computer can read from and write to RAM.

“Temporary Memory” – Short Term

Read Only Memory (ROM):

Memory on the motherboard that is long term; where the specific instructions that are needed for
the computer to operate are stored.
This memory is nonvolatile and your computer can only read from a ROM chip.
The instructions remain on the chip regardless if the power is turned on or off.

“Permanent Memory” – Long Term

• Output devices:
Output devices make the information resulting from the processing available for use. The
two output devices more commonly used are the printer and the computer screen which
is part of the Monitor.
Some Output devices are given below:
Monitor: screen that display information such as text, numbers, and pictures-softcopy.
Printer: gives you information from the computer in printed form – hardcopy.
Speakers: allow you to hear voice, music, and other sounds from your computer.
Modem: allows you to use your computer to communicate with other computers.
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• Storage Devices:
Auxiliary storage devices are used to store data when they are not being used in memory.
The most common types of auxiliary storage used on computers are flash drives, hard
disks, floppy disks and CD-ROM drives, Compact disk (CD), Digital Versatile Disk
(DVD).