COMPUTER HARDWARE.

- Hardware represents the physical and tangible components of a computer, i.e. the components that can
be seen and touched.
- Examples of Hardware are the following −
 Input devices − keyboard, mouse, etc.
 Output devices − printer, monitor, etc.
 Secondary storage devices − Hard disk, CD, DVD, etc.
 Internal components − CPU, motherboard, RAM, etc.

Relationship between Hardware and Software

 Hardware and software are mutually dependent on each other. Both of them must work together to
make a computer produce a useful output.
 Software cannot be utilized without supporting hardware.
 Hardware without a set of programs to operate upon cannot be utilized and is useless.
 To get a particular job done on the computer, relevant software should be loaded into the hardware.
 Hardware is a one-time expense.
 Software development is very expensive and is a continuing expense.
 Different software applications can be loaded on a hardware to run different jobs.
 A software acts as an interface between the user and the hardware.

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- If the hardware is the 'heart' of a computer system, then the software is its 'soul'. Both are complementary
to each other.
- The hardware is categorized in the following:-
1. Input devices
2. Processing (CPU)
3. Storage
4. Output devices

1. Computer Input Devices

- Following are some of the important input devices which are used in a computer −

 Keyboard
 Mouse
 Joy Stick
 Light pen
 Track Ball
 Scanner
 Graphic Tablet
 Microphone

a) Keyboard
- Keyboard is the most common and very popular input device which helps to input data to the computer.
- The layout of the keyboard is like that of traditional typewriter, although there are some additional keys
provided for performing additional functions.

- The keys on the keyboard are as follows −

S. No Keys & Description

Typing Keys
1 These keys include the letter keys (A-Z) and digit keys (09) which generally
give the same layout as that of typewriters.

2 Numeric Keypad

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 It is used to enter the numeric data or cursor movement. Generally, it consists of
a set of 17 keys that are laid out in the same configuration used by most adding
machines and calculators.

Function Keys
3 The twelve function keys are present on the keyboard which are arranged in a
row at the top of the keyboard. Each function key has a unique meaning and is
used for some specific purpose.

Control keys
4 These keys provide cursor and screen control. It includes four directional arrow
keys. Control keys also include Home, End, Insert, Delete, Page Up, Page
Down, Control(Ctrl), Alternate(Alt), Escape(Esc).

Special Purpose Keys

5 Keyboard also contains some special purpose keys such as Enter, Shift, Caps
Lock, Num Lock, Space bar, Tab, and Print Screen.

b) Mouse
- Mouse is the most popular pointing device. It is a very famous cursor-control device having a small palm
size box with a round ball at its base, which senses the movement of the mouse and sends corresponding
signals to the CPU when the mouse buttons are pressed.
- Generally, it has two buttons called the left and the right button and a wheel is present between the
buttons. A mouse can be used to control the position of the cursor on the screen, but it cannot be used to
enter text into the computer.

Advantages

 Easy to use
 Not very expensive
 Moves the cursor faster than the arrow keys of the keyboard.
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 c) Joystick
- Joystick is also a pointing device, which is used to move the cursor position on a monitor screen.
- It is a stick having a spherical ball at its both lower and upper ends.
- The lower spherical ball moves in a socket. The joystick can be moved in all four directions.

- The function of the joystick is similar to that of a mouse.

- It is mainly used in Computer Aided Designing (CAD) and playing computer games.

d) Light Pen
- Light pen is a pointing device similar to a pen.
- It is used to select a displayed menu item or draw pictures on the monitor screen.
- It consists of a photocell and an optical system placed in a small tube.

- When the tip of a light pen is moved over the monitor screen and the pen button is pressed, its photocell
sensing element detects the screen location and sends the corresponding signal to the CPU.
e) Track Ball
- Track ball is an input device that is mostly used in notebook or laptop computer, instead of a mouse.
- This is a ball which is half inserted and by moving fingers on the ball, the pointer can be moved.

- Since the whole device is not moved, a track ball requires less space than a mouse.
- A track ball comes in various shapes like a ball, a button, or a square.

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 f) Scanner
- Scanner is an input device, which works more like a photocopy machine.
- It is used when some information is available on paper and it is to be transferred to the hard disk of the
computer for further manipulation.

- Scanner captures images from the source which are then converted into a digital form that can be stored
on the disk.
- These images can be edited before they are printed.
g) Digitizer
- Digitizer is an input device which converts analog information into digital form.
- Digitizer can convert a signal from the television or camera into a series of numbers that could be stored
in a computer. They can be used by the computer to create a picture of whatever the camera had been
pointed at.

- Digitizer is also known as Tablet or Graphics Tablet as it converts graphics and pictorial data into binary
inputs.
- A graphic tablet as digitizer is used for fine works of drawing and image manipulation applications.

h) Microphone
- Microphone is an input device to input sound that is then stored in a digital form.

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- The microphone is used for various applications such as adding sound to a multimedia presentation or for
mixing music.

i) Bar Code Readers

- Bar Code Reader is a device used for reading bar coded data (data in the form of light and dark lines).
- Bar coded data is generally used in labelling goods, numbering the books, etc.
- It may be a handheld scanner or may be embedded in a stationary scanner.

- Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which is then fed to the
computer that the bar code reader is connected to.

2. Processing - CPU (Central Processing Unit)

- Central Processing Unit (CPU) consists of the following features −

 CPU is considered as the brain of the computer.

 CPU performs all types of data processing operations.
 It stores data, intermediate results, and instructions (program).
 It controls the operation of all parts of the computer.

- CPU itself has following three components.

 Memory or Storage Unit

 Control Unit
 ALU(Arithmetic Logic Unit)
 Registers

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  Control Unit (CU)
- This unit controls the operations of all parts of the computer but does not carry out any actual data
processing operations.
- Functions of this unit are −
 It is responsible for controlling the transfer of data and instructions among other units of a computer.
 It manages and coordinates all the units of the computer.
 It obtains the instructions from the memory, interprets them, and directs the operation of the
computer.
 It communicates with Input/output devices for transfer of data or results from storage.
 It does not process or store data.

 ALU (Arithmetic and Logic Unit)

- This unit consists of two subsections namely,

 Arithmetic Section
 Logic Section

Arithmetic Section

- Function of arithmetic section is to perform arithmetic operations like addition, subtraction,

multiplication, and division.
- All complex operations are done by making repetitive use of the above operations.

Logic Section

- Function of logic section is to perform logic operations such as comparing, selecting, matching, and
merging of data.

3. Computer - Memory
- A memory is just like a human brain. It is used to store data and instructions.
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- Computer memory is the storage space in the computer, where data is to be processed and instructions
required for processing are stored.
Memory is primarily of three types −

 Primary Memory/Main Memory

 Secondary Memory

Primary Memory (Main Memory)

- Primary memory holds only those data and instructions on which the computer is currently working.
- It has a limited capacity and data is lost when power is switched off.
- It is divided into two subcategories RAM and ROM.

Characteristics of Main Memory

 Usually volatile memory.

 Data is lost in case power is switched off.
 It is the working memory of the computer.

Main memory is further sub-divided in to two:-

 Random Access Memory (RAM)

 Read Only Memory (ROM)

 Random Access Memory(RAM)

- RAM (Random Access Memory) is the internal memory of the CPU for storing data, program, and
program result.
- It is a read/write memory which stores data until the machine is working.
- As soon as the machine is switched off, data is erased.

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  Read Only Memory (ROM)
- ROM stands for Read Only Memory. The memory from which we can only read but cannot write on it.
- This type of memory is non-volatile.
- The information is stored permanently in such memories during manufacture.

Secondary Memory

- This type of memory is also known as external memory or non-volatile.

- It is slower than the main memory. These are used for storing data/information permanently.
- For example, disk, CD-ROM, DVD, etc.

Characteristics of Secondary Memory

 These are magnetic and optical memories.

 It is known as the backup memory.
 It is a non-volatile memory.
 Data is permanently stored even if power is switched off.
 It is used for storage of data in a computer.
 Computer may run without the secondary memory.
 Slower than primary memories.

4. Computer - Output Devices

Types of Output devices

a. Monitors
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 b. Graphic Plotter
c. Printer

a. Monitors
- Monitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer.
- There are two kinds of viewing screen used for monitors.
Cathode-Ray Tube (CRT)
Flat-Panel Display

Cathode-Ray Tube (CRT) Monitor

- The CRT display is made up of small picture elements called pixels.
- The smaller the pixels, the better the image clarity or resolution.
- It takes more than one illuminated pixel to form a whole character, such as the letter ‘e’ in the word help.

- There are some disadvantages of CRT −

 Large in Size
 High power consumption

Flat-Panel Display Monitor

- The flat-panel display refers to a class of video devices that have reduced volume, weight and power
requirement in comparison to the CRT.
- You can hang them on walls or wear them on your wrists. Current uses of flat-panel displays include
calculators, video games, monitors, laptop computer, and graphics display.

b. Printers
- Printer is an output device, which is used to print information on paper.

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- There are two types of printers −

 Impact Printers
 Non-Impact Printers

A. Impact Printers
- Impact printers print the characters by striking them on the ribbon, which is then pressed on the paper.
- Characteristics of Impact Printers are the following −

 Very low consumable costs

 Very noisy
 Useful for bulk printing due to low cost
 There is physical contact with the paper to produce an image
- These printers are of two types −

I. Character printers
II. Line printers

I. Character Printers
- Character printers are the printers which print one character at a time.
- These are further divided into two types:

 Dot Matrix Printer(DMP)

 Daisy Wheel

 Dot Matrix Printer

- In the market, one of the most popular printers is Dot Matrix Printer.
- These printers are popular because of their ease of printing and economical price.

Advantages

 Inexpensive
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  Widely Used
 Other language characters can be printed
Disadvantages

 Slow Speed
 Poor Quality

 Daisy Wheel
- Head is lying on a wheel and pins corresponding to characters are like petals of Daisy (flower) which is
why it is called Daisy Wheel Printer.
- These printers are generally used for word-processing in offices that require a few letters to be sent here
and there with very nice quality.

Advantages

 More reliable than DMP

 Better quality
 Fonts of character can be easily changed
Disadvantages

 Slower than DMP

 Noisy
 More expensive than DMP
II. Line Printers
- Line printers are the printers which print one line at a time.

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- These are of two types −

 Drum Printer
 Chain Printer
Advantages

 Very high speed

Disadvantages

 Very expensive
 Characters fonts cannot be changed

 Chain Printer
- In this printer, a chain of character sets is used, hence it is called Chain Printer.
Advantages

 Character fonts can easily be changed.

 Different languages can be used with the same printer.
Disadvantages

 Noisy

B. Non-impact Printers
- Non-impact printers print the characters without using the ribbon.
- These printers print a complete page at a time, thus they are also called as Page Printers.
- These printers are of two types −

 Laser Printers
 Inkjet Printers

Characteristics of Non-impact Printers

 Faster than impact printers

 They are not noisy
 High quality
 Supports many fonts and different character size
 Laser Printers
- These are non-impact page printers. They use laser lights to produce the dots needed to form the
characters to be printed on a page.
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Advantages

 Very high speed

 Very high quality output
 Good graphics quality
 Supports many fonts and different character size
Disadvantages

 Expensive
 Cannot be used to produce multiple copies of a document in a single printing
 Inkjet Printers
- Inkjet printers are non-impact character printers based on a relatively new technology.
- They print characters by spraying small drops of ink onto paper.
- Inkjet printers produce high quality output with presentable features.

- They make less noise because no hammering is done and these have many styles of printing modes
available.
- Color printing is also possible. Some models of Inkjet printers can produce multiple copies of printing
also.
Advantages

 High quality printing

 More reliable
Disadvantages

 Expensive as the cost per page is high

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  Slow as compared to laser printer

Factors considered in hardware selection.

 Processor type and speed.
- The price of a computer is dictated by the micro-processor installed and its clock speed.
 Memory capacity
- This dictates the operating system and the applications that can run effectively on the computer.
 Warrant
- The hardware bought must have a warrant cover and must be guaranteed for a specific period of time.
 Cost
- A good market survey would enable purchase of genuine components at a reasonable cost.
 Compatibility and upgradability
- The hardware bought must be compatible across plat forms and easily upgradable.
 Portability
- Portable computers are ideal for people who do not take most of their time in an office.
 Display
- Flat panel display monitors are becoming more popular and are gradually replacing the traditional
CRT monitors.

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