Computer Hardware
[ From chapter-4 of the book "Information Technology in Banking" written by Abul Kashem Md. Shirin and Nusrat Tamanna Prianka and published by Institute of Bankers, Bangladesh (IBB) ]
Computer
is an electronic device which quickly and accurately processes the data and
information supplied by human using logic and formula given by human to output
result for human being. Human beings undertake decision based on this output.
1. History
of Development of Computer
Computer
is the result of research of hundreds of years. Development of computer starts
with the invention of counting machine by various mathematicians like John
Napier (1550 – 1617), Blasé Pascal (1642) and Leibniz (1671). Charles Babbage
(1792 – 1871), a mathematician of England, developed Difference Engine in 1821.
In 1833, he started developing another counting machine in the name of
“Analytical Engine”, but could not complete before his death. Design of his
Analytical Engine is the basis of modern Computer. This is why Charles Babbage
is terms as the “Father of Computer”.
Professor
D. John Atanasoff of United States developed an electronic Computer named ABC
using vacuum tube in 1942. Later on in 1946, Professor Dr. John Mauchly and his
student Engineer Presper jointly developed a computer named ENIAC (Electronic
Numeric Integrator And Calculator) on which there were 1800 valves. Its weight
was 30 tons, and an electric load of 150 KW was required to run it. These two
scientists developed another computer in the name of UNIVAC (Universal
Automatic Calculator) in 1951 which had Input, Output and Memory units. This
was the first electronic computer produced commercially.
In
1954, the IBM (International Business Machine) company of United States
produced a Computer in the name of IMB-701 and starts business.
Bangladesh
Atomic Energy Commission installed first computer in Dhaka in 1964. It was an
IBM-1620 mainframe computer. Thereafter Bangladesh University of Engineering
& Technology (BUET), Bangladesh Bureau of Statistics, Power Development
Board installed mainframe computer for their uses.
In
1971, the Intel Company of United States developed MSC-4 microprocessor and
introduced Microcomputer.
Due
to its development and commercial availability, we can see the use of
Microcomputers in educational institutions, business organizations, offices and
houses.
2. Generations
of Computer
Computer
can be divided into following four generations:
1st
Generation (1951 – 1958):
Characteristics:
Use of Vacuum Tube or Vacuum Valve, Big in size, Capability to store program
and information, Use of Magnetic Drum, Punch Card and Magnetic tape. Example:
ENIAC, MARK, IBM-650.
2nd
Generation (1958 – 1965):
Characteristics:
Use of IC (Integrated Circuit), Use of transistor instead of Vacuum Tube, Small
in size, introduction of ACCII code, development of high-level language like
COBOL, FORTRAN and ALGOL. Example: IBM-1620, CDC-1604, NCR-300.
3rd
Generation (1965 – 1971):
Characteristics:
Introduction of Mouse as input device, Small in size, reduction of price,
Introduction of VDO unit and Printer as output device, use of secondary memory,
invention of BASIC language, word processing and other applications. Example:
IBM-370, PDP-II.
4th
Generation (1971 – to date):
Characteristics:
Invention and use of Microprocessor, Semi-Conductor memory, ROM, RAM, PROM,
EPROM, Higher capacity of storing information, Development of operating systems
like DOS, MAC, Windows and Unix, development of various application software
and programming languages, development of Super Computer, Laptop, Notebook,
Desktop and Personal Computers. Example: PC, Sever and Laptop of various brands
such as IBM, Compaq, HP, Sun, Dell, ACER.
3. Types
of Computer
Based
on the nature of jobs, the Computer can be divided into following three types:
1. Analog Computer
2. Digital Computer
3. Hybrid Computer
Analog
Computer is used for special purposes such as measuring pressure and
temperature, supply of petrol in petrol pumps and determining price, and
controlling speed of a vehicle or Airplane.
Digital
Computer works in line with the principles of mathematics. It works using
binary systems, i.e., using 1 and 0. The Computers we use at home and office
are all Digital computers.
Hybrid
Computer collects data from various systems using analog process, but processes
the data in digital system.
Based
on size and capacity, Computers (or Digital Computers) can be divided into four
types as under:
1. Super Computer
2. Mainframe Computer
3. Mini Computer
4. Micro Computer
Super
Computer is very powerful. It requires less time to complete mathematical
processes. Super computer is used in scientific research, for processing of
large volume of data, for controlling missile, space research, design of
nuclear plant. CRAY-1, Super SxII, CYBER-205 are the example of Super
Computers.
Mainframe
Computer is very large in size. Connecting many small computers into it, many
people can work together in a Mainframe Computer. It is used in large
organizations like Banks, Insurance Companies and Universities. IBM4300, UNIVAC
1100, NCR 8370 are the example of Mainframe Computers.
Mini
Computers are smaller and less costly than Mainframe Computers. Many people can
also work in a Mini Computer together using terminals connected to it.
Relatively smaller Banks, Insurance Companies, Industries, Educational
Institutions and Research Organizations use Mini Computers. IBM S/34 and NCR
S/9290 are the example of Mini Computers.
Microcomputers
are very small, cheap and widely used computer. As microprocessor is used in
this type of computers, they are termed as Microcomputer. Only one person can
work at a time in a Microcomputer. For this they are also known as Personal
Computer or PC. Microcomputers are used at home and office for personal and
official purposes. They are also used for entertainment purposes like playing
games, viewing video, listening songs, and browsing internet. IBM PC, Apple PC
and Macintosh PC are the example of Microcomputers.
4. Computer
Hardware and Devices
The
devices of a computer may be divided into five parts, like:
Input devices
Output devices
Processing devices
Memory devices
Special devices
4.1. Input
devices
The
devices or parts of the computer used for inputting information, data and
instruction into the computer are known as Input Devices. Keyboard, Mouse,
Joystick, Scanner, Digital Camera, Microphone etc are the example of input
devices.
Keyboard: A Keyboard is a device that contains 104 to 110
number of keys. These keys are used for typing letters and digits and providing
instructions to the computer. A keyboard is connected to the motherboard of a
computer using a cable.
Mouse: A Mouse is a device used as alternative or associated equipment for
providing instruction to the computer having windows or Macintosh operating
system in it. The mouse has 2 or 3 buttons.
4.2. Output
devices
The
devices which are used for communicating result to the users are called Output
Devices. Monitor, Printer, Speaker and Plotter are the example of output
devices.
Monitor: The result of processing activities on certain supplied
information and data is displayed using text, graph or picture on a TV like
device called Monitor. The Monitor is connected to the system board of a
computer using a data cable. In some monitors, a separate power connection is
required.
Printer: The output of a computer is printed on paper using a
device called Printer. Printer is connected to the computer’s system board
using a data cable. Power is supplied to the printer using another cable.
Printer
is of two types – Dot Matrix Printer and Laser Printer. Dot matrix printer has
a “Head” which creates impact on a ribbon. The ink on the ribbon produces
letter, special character and digit on the paper. Epson dot matrix printer,
Epson line printer are the example of dot matrix printer. In the Laser Printer
instead of Head, laser ray is used to produce letter, special character and
digits. Ina Laser Printer, instead of ribbon, a Tonner or Cartridge is used for
supplying ink. Ink Jet Printer and Canon Laser Printer are the example of Laser
Printer.
Speaker: Speaker is used for creation of sound during
listening songs or viewing video.
Plotter: A Plotter is used for printing a drawing from
computer. Plotter is also used for printing large picture, poster, calendar and
map.
4.3. Processing
Devices
The
devices used for processing of supplied information, data and instructions in a
computer are called Processing Devices. CPU or Central Processing Unit is a
processing device used in computer. It performs all the processing activities
of a computer. CUP is like the brain of human being. The speed and capacity of
processing of a computer depends on its CPU.
In
1971, the Intel Company invented microprocessor for use in computer. It was
called as 8008 microprocessor. Thereafter Apple produced microprocessor in 1976
and IBM in 1981.
The
functionalities of a CPU are stated below:
1. CPU sends controlling and time determining signals to
all parts of the computer.
2. Send and receive data between memory and input/output
devices.
3. Receive data and instructions from memory.
4. Decode the instructions.
5. Perform mathematical and logical activities.
6. Run program
from computer memory.
7. Coordinate between input and output devices.
Based
on the architecture, a microprocessor can be divided into 2 groups like CISC
processor and RISC processor.
CISC
or Complex Instruction Set Computer is a microprocessor which uses microcode.
Microcode consists of some instructions (software program) which work from
inside the chip. As this type of microprocessor run by software, they are
normally slow. Examples of CISC microprocessor are: 8085, 8086, 8088, 80286,
80386SX, 80386DX, 80486SX, 80486DX and Pentium of Intel, 386DX, 486DX of AMD,
6800, 68000, 68040 of Motorola.
RISC
or Reduced Instruction Set Computer is a microprocessor in which less number of
instructions sets are used. It is not software based, rather hardware based and
as such faster than the CISC processor. Banks normally uses RISC
processor-based computers as its main database server in the data center. Unix
is normally used as operating system of such RISC servers. For example, AIX is
used as operating system for IBM RISC servers, Sun Solaris for SUN RISC servers
and HP-UX for HP RISC servers.
4.4. Memory
Device
Memory
devices are the devices where the computer temporarily or permanently stores
the data before, during and after processing. The memory devices can be
categorized into 3 groups: Primary or Main memory, Cache memory and Secondary
or Auxiliary memory.
4.4.1. Primary
or Main memory
The
memory directly connected to the CPU is called Primary or Main Memory. It is
used to store program, data, instructions and result during execution. RAM and
ROM are the example of such memory.
RAM: RAM stands for Random Access Memory. Computer read all the relevant
data, program and instructions from the input devices or permanent storage and
writes into the RAM for processing. RAM has the following characteristics:
1. RAM is volatile in nature
2. It is a read-write memory
3. During processing the information stay in RAM
4. If power fails, all the information removes from the
RAM.
ROM: ROM stands for Read Only Memory. ROM stores a program called BIOS
(Basic Input Output System). List, position and specification of all the
devices of a computer are recorded into the BIOS. Computer at the time of
startup recognizes all the devices with the help of BIOS. The characteristics
of a ROM are as under:
1. ROM is a permanent main memory.
2. The information in the ROM can only be read, can’t be
modified.
3. The programs required to startup a computer are stored
permanently in the ROM
4. If power fails, the information at ROM does not
vanish.
4.4.2. Secondary
or Auxiliary memory
The
memory which is used to store the user program and information permanently is
called Secondary or Auxiliary memory. Examples are: Floppy Disk, Hard Disk,
Compact Disk, Magnetic Tape, Pen Drive etc.
Floppy Disk: A light and small disk which is produced by putting
a magnetic layer on a thin plastic sheet is called Floppy Disk. The information
and program are stored in Floppy Disk. Normally floppy disk is used to transfer
information from one computer to another. Floppy disks are of two sizes – 3.5”
and 5.25”. The device used to read and write information from/to floppy disk is
called Floppy Drive. Floppy Drives are also available in two sizes – 3.5” and
5.25”.
The
capacity of the 3.5” floppy disk is 1.44 MB and that of 5.25” floppy drive is
360 KB.
Due
to invention of Pen Drive, the use of Floppy Drive has become unpopular.
Hard Disk: A hard disk is connected inside the computer box
using screw and data & power cables, and has much higher capacity and speed
than the floppy disk. The data and programs are normally kept stored into the
hard disk. No drive is required in the computer for use of hard disk. Hard disk
of various capacity is available in the market like 250 GB hard disk, 500 GB
hard disk etc.
Compact Disk: Compact Disk is called CD in short. CD is used for
recording or storing data, program, song, game, video etc. and also for
transferring data from one computer to another. Some CD only allows reading
Information from it. The information in it can’t be modified. Also new
information can’t be added into these CD. These CDs are called CD-ROM (Read
Only Memory). The drive connected to the Computer and used to read information
from CD is called CD Drive. There are some CDs which allow reading, modifying
and adding information. These CDs are called Re-Writable CD (CD-RW). For
reading, modifying and adding information into a CD-RW, a device is connected
with the computer which is called CD Writer. A CD is like a circular disk
having a diameter of 4.75”. A CD has a capacity of 650 MB.
Magnetic Tape: Magnetic Tape is a plastic reel covered with iron
oxide and wrapped in a cassette. Magnetic Tape is used for backing up useful
data from hard disk to the tape. This ensures that the data will be available
in case of damage of the hard disk. Making duplication of data from hard disk
into a magnetic tape is called Backup. Bank daily creates a makeup copy of
customer data. A device is connected with the computer using a data cable and
used to copy data from computer hard disk to tape drive. This device is called
as Tape Drive.
Pen Drive: A Pen Drive is a data storage device which is
physically much smaller than a floppy disk but can store mush higher capacity
of data like 2GB, 4GB, 8GB and up to 256 GB. They are more durable and reliable
because of their lack of moving parts. A Pen Drive is also called as USB flash
drive because it is equipped with a USB (Universal Serial Bus) connector at one
end. The connector is inserted into the USB port on a computer and the files or
data can be copied from/to the pen drive.
4.4.3. Cache
memory
A
special memory placed with the CPU or main memory to increase speed of
processing is called Cache Memory. Cache Memory can be classified into two
types – Internal Cache and External Cache. Internal Cache is placed inside the
microprocessor whereas the external cache is placed on the mother board as IC
(Integrated Circuit).
4.5. Special
Devices
Special
devices are devices used to interconnect input, output and memory devices.
System Box, Mother Board, Power Supply Unit are the example of special devices.
System Box: A box where the mother board, hard disk, floppy
disk, CD drive and power supply unit are connected using screw and cable, is
called System Box. Many people wrongly call the system box as CPU. A system box
connected with all the required devices, a monitor, a keyboard and a mouse
constitute a computer.
Mother Board: A device which is connected to the system box using
screw and which has various slots over which the CPU (processor), ROM and RAM
are connected directly, is called Mother Board. The Mother Board has also
various ports to which the keyboard, mouse, monitor, floppy drive, CD drive and
printer are connected using cable. There are thousands of wires placed inside
the mother board which connects various devices internally and carry data and
signal from one device to another device. These wire system is called Bus
System.
Power Supply Unit: A Power Supply Unit is the component that supplies
power to the other components in a computer. More specifically, a power supply
unit is typically designed to convert Alternating Current (AC) to Direct
Current (DC) which is required for the various components of the computer.
UPS: UPS stands for Uninterrupted Power Supply. UPS is an electrical
apparatus that provides emergency power to a computer when the input power
source fails, thus protect Computer from sudden shutdown. The UPS can be of two
types – Online UPS and Offline UPS. Online UPS has zero transfer time and used
with servers, while the offline UPS has a transfer time of 5-10 ms. Both the
types of UPS can protect the computer from shutting down in case of power
failure, but the online UPS, in addition, can protect data from being garbage/damaged
due to power fluctuations as this type of UPS require no transfer time for
switching between main power to batter power.
Voltage Stabilizer: A Voltage Stabilizer is an electric regulator
designed to automatically maintain an output of constant voltage level
irrespective of variation in input voltage. The Voltage Stabilizers are used
with Computer System to protect the computer from sudden fluctuation of
voltage.
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