Download ONORUESE GODS FAVOUR OGHENETEJIRI ACCOUNTING

ONORUESE GODS FAVOUR OGHENETEJIRI
ACCOUNTING DEPARTMENT
GST115--(INFORMATION AND COMMUNICATION TECHNOLOGY)
SIX CATEGORIES OF COMPUTER HARDWARE
A computer hardware refers to the physical components of the computer system; the parts we
can touch or break. The computer hardware components can be grouped into six different
categories, they are:
1) Central processing unit (CPU)
2) Main memory
3) Secondary storage
4) Input devices
5) Output devices
6) Connectivity hardware
CENTRAL PROCESSING UNIT (CPU)
The CPU is the most important component of a computer system. It is the brain and heart of the
computer, it determines the capacity of the computer system, and it is also the only part of the
computer system that can work on its own. It connects other components and directs them
according to the available program. Reasoning, decision making and arithmetic operations are
prior functions of CPU. In fact, No CPU means no computer system. The CPU has 2 major parts;
the arithmetic and logic unit (ALU) and control unit (CU). These 2 CPU parts contain registers.
Registers are high speed storage locations that temporarily hold data and instruction during
processing.
The Arithmetic and logic unit (ALU) is the part of the CPU which handles arithmetic operations
such as addition, subtraction, multiplication and division. The ALU has the ability to carry out
reasoning and decision making, thus performs logical operations such as greater than(>), less than
(<), equal to(=), etc. The ALU has 2 registers namely; Adder and Accumulator.
The control unit interprets the instructions from the main memory. It gives instructions to ALU on
what operations and how to carry it out. It gives directives to the peripheral devices of the
computer system. The control unit controls all the activities of the computer system. Control units
have 3 registers namely; instruction register, instruction decoder, program counter.
THE MAIN MEMORY
The main memory is a storage media on the motherboard. It is used to store data and instruction to
be executed by the CPU. Main memory is closer to the CPU than any secondary storage device.
The main memory of a computer system can be classified into 3 distinct categories which are
discussed briefly below.
Random Access Memory(RAM);
This is a volatile type of memory. In case of power failure, information on RAM is lost. It is a
temporary storage medium used to hold the data and instruction currently working on by the
computer system. It is a storage device in which users interact with most often, it is also erasable.
Example, when you are typing on system in Microsoft word, you working on RAM when the
information typed is not saved, it is lost in case of power failure.
Read Only Memory (ROM);
This is a type of main memory, it is non-volatile, power failure does not affect its content. Users
can read the content but cannot change it or write to it. It is used to store permanent instructions
that control the activities of the computer system. Nevertheless, there are ways to change the
content of specific kind of ROM, example, the EEPROM( Electrically Erasable Programmable
Read-only Memory) allows user to change its content repeatedly through the use of higher than
normal electrical voltage.
Complementary Metal oxide semiconductor Memory (CMOS)
This is a hybrid memory derived from combination of some properties of RAM and ROM. It is
non-volatile and the content can be easily changed, it is often used to store configuration
information of computer system like size of hard disk, current time and date it does not store any
program.
SECONDARY STORAGE;
Secondary storage devices are devices that store the information on RAM since RAM is volatile to
prevent loss of information. There are 3 secondary storage devices namely;
Magnetic Media: floppy disk, hard disk, and magnetic tape are good examples of magnetic media.
I)
Floppy disk: This has a square shape. The protective square case houses a round piece
of flexible plastic disk with a magnetic coating. It is portable and has a very small
size of 1.44 MB. The reading and writing speed is very slow and it is not durable.
They are not common these days because of the associated disadvantages. Though
there are new kinds of floppy disk with bigger capacity and better durability but they
require special drive to drive them and thus they are not popular. Examples include
Zip Disk(up to 750MB).
II)
Hard disk: This is a very huge type of memory and it is one of the factor that
determines how powerful a computer system is. It contains a set of circular plates
made of metal with a magnetic coating. It rotates at a very high speed. When data is
to be read from a hard disk, the computer gives the disk address and the hard disk
will go to specific location to read the data.
III)
Magnetic tape: This is a magnetically coated strip of plastic on which data are stored.
Large amount of data can be stored on it and it is very cheap. It requires a tape drive
to read and write data on a tape, it is a slow storage device mainly used for long term
storage and backup.
Optical Media: These are storage media that hold content in digital form and that are written
and read by a laser. These storage media group include all the various CD and DVD
variations.
I)
Compact Disk (CD): CD is a round plastic disk with a metal coating. It uses laser
technology for storing and accessing data. CD can be classified further into i)
CD-ROM group which can store up to 640MB of data and once it is written to, the
content cannot be changed or over written, it is cheap. Data in CD-ROM are read
using CD-ROM drive. ii) CD-R(CD Recordable), this is very common in the
II)
III)
market, it allows users to write data into it but only once, it is durable if well kept and
can store up to 640MB. iii) CD-RW (CD Rewriteable) it can also store up to 640 MB
of data. Data can be written and over written for many times.
Digital Versatile Disk(DVD): This is an advanced optical storage media. It has a
diameter and thickness similar to the CD but it has a much higher capacity. DVD can
be classified into i) DVD ROM which has a higher capacity from 4.7GB to 17GB, It
makes use of DVD ROM drive to read data stored on it. ii) DVD-R which works like
CDR but has a higher capacity. User can write very large volume of data into it but
once written, it cannot be over written or changed. iii ) DVD-RW which is similar to
CD-RW but has a higher capacity. Iv) Magneto Optical Disk which combines both
magnetic and optical methods to store data, it is more reliable than DVD and can be
rewritten for infinite number of times.
Semi conducting Media: These are often called flash memory, they are used to store
data, they are very reliable and durable, they are silent in operation and they are used
in some portable devices such as MP3. Examples include: secure digital card(SD
card).
INPUT DEVICES
These are devices that allow users to enter data into the computer system. Examples are i)
keyboard; which allows user to key in characters into the computer system. ii) mouse; which
is a pointing device used to point and select items on the screen, it looks like a rat in shape, it
works by the point and click principle and there are 2 types namely mechanical and optical
mouse. There are other examples of input devices which include; track ball, joystick/joypad,
Graphics tablet, Touch screen, Image Scanner, digital video, voice input etc
OUTPUT DEVICES
An output device is a hardware that presents digital information in a form that human being
can understand. Examples include; i) Visual Display Unit(VDU) which is commonly referred
to as monitor, there are two types of VDU namely; cathode ray tubes and liquid crystal display.
Other examples include; Data projector, printer, audio output device etc.
CONNECTIVITY HARDWARE
Connectivity hardware is the hardware that allows computer to be physically connected to
different types of networks. Common connectivity hardware include; connectors, network
interface card, modem, repeater, hubs, bridges, multiplexer, router, brouter, gateways etc.