COMPUTER SYSTEM

1.1 INTRODUCTION OF COMPUTER

• The word ‘Computer ‘is derived from the Latin word ‘Computare’.

• An electronic device that can perform any kind of work involving arithmetic and logical

operations on data.

• A fast and accurate electronic programmable device that accepts data and instructions, processes them as the instructions, and produces information as an output.

CHARACTERISTICS OF COMPUTER

• Speed: process tasks at high speed.

• Accuracy: 100% accurate if there is no GIGO and bugs.

• Automatic: No need to instruct once the instructions are fed.

• Storage: Stores data in the form of binary digits and can has a huge storage capacity.

• Diligence: Capable of performing tasks repeatedly without losing efficiency.

• Versatility: Capability of doing various kinds of tasks

• Reliability

• No Intelligence: cannot take its own decision

• No Feeling

APPLICATION OF COMPUTERS

• OFFICE

• BANKING

• BUSINESS

• E-GOVERNANCE

• COMMUNICATION

• TRANSPORTATION

• EDUCATION

• INDURSTRY

• HEALTH

• ENTERTAINMENT

APPLICATION OF COMPUTERS

·       OFFICE

– To prepare, store and retrieve data as electronic files.

– To handle correspondence and office communications.

– To facilitate administrative work and prepare papers.

– To assist in decision making.

·       BANKING

– To control the entire baking system.

– To maintain customers’ accounts. Computers help to calculate payments, interest, and balance of customers.

– To provide online banking services like internet banking, money transferring, SMS (Short Message Service) banking, mobile banking, ABBS (Any Branch Banking Service), etc. to customers.

– To provide electronic banking services like Automated Teller Machine (ATM).

– To supervise the entire banking activities.

·       BUSINESS

– To manage financial transaction,

– To provide Security,

– To manage stock,

– To boost e-commerce.

– To boost the business by creating websites, ads, etc.,

– To provide communication facilities like email and instant messaging,

– To create documents and reports,

– To give information and provide training to employees.

·       E-GOVERNANCE

– To facilitate access to government information, services, and products.

– To promote civic engagement by allowing citizens to interact with government officials.

– To make the government more accountable by making its operations more transparent and thus reducing the opportunities for corruption.

– To provide opportunities for development, particularly to rural and traditionally underserved communities.

– To establish a paperless working system.

– To increase public participation in the policy and decision-making processes of government.

·       COMMUNICATION

– To do fast and economic communication.

– To communicate among people at different locations.

·       TRANSPORTATION

– To controlling traffics

– To provide information and reservation facilities to people.

– To track vehicles

– To guiding drivers.

EDUCATION

– To increase access to education.

– To improve the quality of teaching and learning.

– To improve knowledge sharing.

– To increase the efficiency and effectiveness in administration and classrooms.

– To prepare notes, reports, and presentations of lectures.

– To facilitate distance learning education.

– To conduct online examinations.

·       INDURSTRY

– controlling the quality of products,

– controlling/operating heavy machines and tools,

– performing dangerous tasks.

– detecting specific errors or defects that occurred in the process.

·       HEALTH

– To assist doctors

– To monitor the condition of patients

– To record the necessary information of patients

– To diagnose diseases in patients.

·       ENTERTAINMENT

– To entertain people of all ages.

– To compose music and set tunes.

– To put special effects in movies.

– To edit songs and movies.

1.1.2 EVOLUTION OF COMPUTER TECHNOLOGY

Harvard Mark-I (1937-1944)

·       1st electromechanical computer developed in the leadership of Howard Aiken with IBM engineers.

·       Named as IBM Automatic Sequence Controlled Computer (ASCC).

·       Consists of mechanical switches and could perform arithmetic operations.

·       as well as solve more complex equations.

·       8 feet high, 51 feet long and 2 feet wide and weighed 35 tons.

Atanasoff Berry Computer (ABC)

·       Developed by John Vincent Atanasoff and Clifford Berry in 1937-1942

·       1st workable machine that had used binary number system.

·       Could solve 29 simultaneous equations.

• Z3 computer

·       Electro-mechanical computer designed by Knorad Zuse in 1941 AD

·       Fully automatic first working programmable computing machine.

Electronic Computers Era

• Based on electron tubes/vacuum tubes or valves, and transistors.

• ENIAC, EDVAC, EDSAC, UNIVAC, ENIAC

First Generation Computers (1943-1958)

• Vacuum tube as the main electronic component.

• Magnetic drum as primary storage.

• Punched cards and paper tape as input and output devices.

• Magnetic tape as secondary memory.

• Large but slow in operation and could perform tasks in milliseconds.

• Consume a very high amount of electricity and produced too much heat.

• No OS and had to setup manually.

• Programmed in machine language.

 

Vacuum Tube

• Developed by John Ambrose Fleming in 1904 AD

• More improved vacuum tube was developed by Lee De Forest in 1906 AD.

• Used as a switch or an amplifier in the early computers.

• A vacuum sealed glass container consists of Cathode, Anode and Grid.

Second generation computers (1959-1964)

• Transistors as the main electronic components.

• Magnetic cores for internal memory and magnetic tapes and disks for external storage.

• Also used punched cards and paper tape for external storage.

• Smaller, more reliable, and more powerful than the first-generation computers.

• Consumed less electricity and generated less heat than the first-generation computers.

• Punched cards as an input device and printers as an output device.

• faster than 1st generation and could perform tasks in microseconds.

• Could be programmed in assembly and high-level languages such as COBOL (Common Business-Oriented Language), FORTRAN (Formula Translator), and ALGOL (Algorithmic Language).

 

Transistor (Transfer Resistance)

• A small device invented by John Bardeen, Walter Brattain, and William Shockley at the Bell Laboratories on December 23, 1947.

• Made up of semiconductor materials like silicon and germanium.

• Used to control the amount of current or voltage or used for amplification/modulation or switching of an electronic signal.

• Smaller than a vacuum tube and has a higher operating speed.

• Can do the work of 1000 vacuum tubes.

Third Generation Computers (1965-1974)

• Integrated circuits as the main electronic components.

• Semiconductor memory for the internal storage medium and magnetic tape, magnetic disk (i.e., floppy disk, hard disk) for the secondary storage.

• Faster than 2nd generation and could performed tasks in a nanosecond.

• Keyboards as an input device and monitors as an output device.

• Operating systems. & could run different programs.

• More reliable and better in performance.

• Could be programmed in high level languages like FORTAN, COBOL, PASCAL, C, C++, etc.

Integrated Circuit (IC)

• used in a variety of devices, including microprocessors, audio and video equipment, and automobiles.

• Developed by Jack Kilby and Robert Noyce in 1958 AD.

• A miniaturized electronic circuit that contains several transistors and other electronic components like resistors, capacitors, etc. on a single wafer or silicon.

Fourth Generation Computers (1975 And onwards)

• VLSIs (microprocessor) and LSIs as the main electronic components.

• Magnetic tape, magnetic disk, optical disk (CD/DVD/Blu-ray), flash memory and SSD for external storage.

• Semiconductor memories for internal memory.

• Advanced input/output devices like mouse, touch screen, LCD, LED, Colour Printer, etc.

• Used GUI-based operating system

• Microcomputers (personal computers) are introduced.

• Laptop and palmtop computers are also developed in this generation.

• Processing speed is increased and measured in a picosecond.

• More versatile, diligent, and reliable.

• They can understand billions of instructions within a second.

• High level languages (i.e., 4th generation languages).

Microprocessor (VLSI)

• An integrated circuit that consists of millions of transistors on a single silicon chip.

• Executes instructions and carries out arithmetic and logical operations.

• Can be of 4-bit, 8-bit, 16-bit, 32-bit, and 64-bit.

• The first microprocessor, ‘Intel 4004’, which was developed by Marcian Ted Hoff of Intel Corporation in 1971 AD, was a 4 bit and had 2300 transistors.

• The Core 2 Duo microprocessor contains more than 2.9 billion transistors on it.

• Speed of a microprocessor is measured in clock speed i.e., Hertz (Hz).

5th Generation Computer (Present and Beyond)

• Will be based on ULSI technology.

• Will have artificial intelligence and be able to think and understand human languages.

• Will have a faster and larger primary memory.

• Will have multiprocessors and parallel processing capacity.

• Will be faster than their predecessors and the processing speed will be measured in femtoseconds.

• Will have larger primary and secondary storage as compared to their predecessors.

 

1.1.3 MEASURMENT UNIT OF PROCESSING SPEED AND STORAGE UNIT

• The processing speed of a computer is measured in fractions of a second.

• The processing speed of a computer can also be measured in hertz.

• The storage capacity of a computer memory or storage device is measured in bytes or higher units of bytes.

• The storage capacity of a computer memory or storage device is measured in bytes or higher units of bytes.

1.1.4 ANALOG, DIGITAL and HYBRID COMPUTERS

• Analog computer

– A special purpose computer that can process only analog data (continuous varying physical quantities like temperature, pressure, speed, depth, height, voltage, etc.).

– Cannot be reprogram.

– Perform operations in parallel.

• Digital computer

– Accept discrete data (discontinuous data) like letters, numbers, symbols, figures, etc. and process them.

– Perform operations in sequential order.

– Can be reprogrammed.

– Versatile and diligence.

• Hybrid Computer

– A special purpose computer that has the capabilities of both digital and analog computers.

– Can convert analog data to digital data and vice versa.

– Used mainly in specialized applications where both kinds of data (continuous and discrete data) need to be processed.

1.1.5 MOBILE COMPUTING AND ITS APPLICATION

• A technology that allows the transmission of data, voice and video through a computer or any other wireless enabled device.

• Application of mobile computing includes email, web browsing, messaging, e-commerce, educational services, Emergency services, entertainment services and global position system.

Features of Mobile Computing device are:

·       It is a portable device that can be used during mobility.

·       It has limited processing and storage capability.

·       It includes mobile communication, mobile hardware, and mobile software.

·       It usually contains a touch screen for providing input. It contains an on-screen or virtual keyboard for proving text inputs. However, an external keyboard can be connected by using the USB port, infrared, or Bluetooth.

·       It contains a camera, speaker, and microphone.

·       It contains handwriting recognizing software.

·       Most of the mobile computing devices contain a memory card slot to expand the storage capacity.

·       It has wireless connectivity such as Bluetooth, Wi-Fi to connect the Internet or with other computing devices as well as a wired connection through the USB port.

·       The most mobile computing device can synchronize their data with applications on users' computers.

·       It can be used for cloud computing and remote access.

·       It uses a mobile computing operating system such as Android, iOS, Windows Mobile OS, Palm OS.

·       It can include GPS (Global Positioning System) receiver for navigation.

Advantages of Mobile Computing

·       It enables users to work from any location at any time.

·       It saves time for accessing data and information.

·       It helps to increase the productivity of users reducing the time and cost.

·       It has made research easier.

·       It is one of the major handheld sources of entertainment of users at present.

·       Nowadays, Business processes are easily available through secured mobile connections.

·       It is portable.

·       It supports cloud computing.

·       It provides remote access to the organizational data from any location.

·       It is an independent platform. It can be accessed from any hardware or software.

 

Disadvantages of Mobile Technology

·       Mobile technology requires faster and quality connectivity services that need either Wi-Fi or GPRS or 3G or 4G connectivity.

·       It has security concerns; most wireless connectivity is unsafe.

·       Large power consumption due to the use of batteries continuously and they do not tend to last long.

·       The danger of misrepresentation i.e., credential verification is a problem.

·       Extensive use of mobile devices results in health problems.

 

1.2 COMPUTER SYSTEM AND I/O DEVICES

• A functional unit in which a group of integrated hardware works together with software to fulfil the purposes of the instructions or programs.

• A combination of different hardware and software that work together to process data according to the instructions given by the user to give information.

• To accomplish the basic operations, different hardware components like input/output unit, CPU, and memory unit are involved in the computer system.

• These different components of a computer are interconnected through buses which transmit Data, instructions, and electric signals from one unit to another.

COMPUTER ARCHITECTURE

• the conceptual structural design and fundamental operational structure of a computer system.

• the conceptual design of different components of a computer system that defines how the different components of the computer system are connected to each other.

• deals with how to design a circuit for hardware components required for building a computer and integrate those components to achieve functionality and performance.

Computer Organization

• the components from which a computer is built.

• the operational units and their interconnections that realize the architecture specification.

• deals with the physical components of a computer system that interact with each other to perform various functionalities.

• deals with physical aspects of computers like circuit designs, memory and its types, microprocessor design, etc.

BLOCK DIAGRAM OF COMPUTER SYSTEM

COMPONENTS OF COMPUTER SYSTEM

• Every computer system has four basics components. They are:

a) Input Unit

b) Processing Unit

c) Output Unit

d) Storage

Input Unit

• A device or unit through which data and instructions are fed into the computer system.

• Accepts or reads data and instructions from a user in human understandable form.

• Converts these inputs in the computer acceptable form i.e., binary code.

• Transfers the converted inputs into the computer system.

Processing Unit

• Refers to CPU, which is composed of ALU, CU and Registers/Memory Unit.

• ALU is the part of the CPU where processing tasks (arithmetic and logical operations) are performed.

• CU is the part of the CPU that controls and directs all the components of the computer.

• A resister is the part of CPU that stores data and instructions temporarily which are currently being used in the computer.

Output Unit

• A device or unit that displays or presents data, results of processing and other information to the users in human understandable form.

• Accepts the results of processing which is in binary coded form.

• Converts binary coded form results into human understandable form.

• Presents the converted results to the users.

Storage Unit

• A component of a computer that stores data, information, programs temporarily or permanently.

• Primary and Secondary memory are the two types of Storage.

• Primary memory is the internal memory, which is accessible directly by the CPU and it stores data and instructions input by a user, intermediate result of processing, results of processing and currently running programs.

• Secondary memory stores data and programs permanently and is not accessible directly by the CPU.

 Microprocessor

• Is an integrated circuit that contains millions of transistors (i.e., electronic components) packed onto a single chip.

• executes instructions of a program, carries out arithmetic and logical operations, and controls other components of a computer.

• is known as the brain of the computer.

• The power and performance of a microprocessor basically, depend on word length (address bus), the number of transistors, and clock speed.

• More number of transistors or electronic components on a microprocessor, more the number of instructions sets.

• More the instruction sets, more the commands or instructions that a microprocessor can understand and work on.

• A word length refers to the number of bits of data bus that can be moved between storage and the processor.

• The word length determines the number of bits processed in a single instruction. More word length means a wider address and data bus and more amount of data processed at a time.

• The clock speed of a microprocessor refers to the capability of executing instructions per second by a processor and is measured in megahertz (MHz).

Component of Microprocessor

a. Bus Interface Unit

b. Prefetch Unit

c. Segment and Paging Unit

d. Decode Unit

e. Execution Unit

f. Cache memory (L1)

Bus Interface Unit

• BIU is the part of the microprocessor that links the CPU with the other components of a computer.

• It handles all the transfer of control signals, data and addresses on the buses for the execution unit (EU).

• It sends out addresses, fetches instructions from memory, reads data from ports and memory, and writes data to ports and memory.

 

Execution Unit

• EU receives program instruction codes and data from the bus interface unit, executes them, and stores the results in the general registers.

• It can also store the data in a memory location or send it to an I/O device by passing the data back to the BIU.

• it receives and outputs all its data through BIU.

• It has four subunits: arithmetic logic unit, registers, control unit, and protection test unit.

• The ALU performs arithmetic and logical operations on data.

• A register holds instructions, storage addresses, and data that are currently being used in a computer.

• The control unit (CU) controls the flow of data through the processor and coordinates the activities of the other units within it.

• The Protection Test Unit acts as a traffic constable and verifies the address of the data which is sent by the Control Unit from the Decode Unit. It makes sure that every operation is done in the right way.

 

Prefetch Unit

• decides and instructs the BIU to retrieve data and instructions from the main memory (RAM).

• queues instructions to assure that the microprocessor is in continuous operation. Segment and Paging Unit (memory management unit)

• converts internal logic addresses into external memory addresses.

 

Decode Unit

• decodes or translates instructions into a simple format understood by the ALU and registers. It makes processing more efficient.

 

Function of Microprocessor

• Supervises and controls I/O devices.

• Transferring data between memory and I/O devices

• Fetching instructions from the main memory

• Decoding instruction to determine what action is required to be done.

• Fetching required data from the main memory or I/O devices based on fetched instruction.

• Performing arithmetical and logical operations

• Transferring the results of execution to memory or an output device

• Executing programs stored in memory

• Performing communication among the I/O devices etc.

1.2.4 SYSTEM BUS

•It is an electric pathway or communication path that interconnects different components of a computer system and through which data, instructions, and electric signals are transmitted from one device to another.

• is the lining of wires through which bits are transmitted between the components of a computer system.

• Can be 8-bit, 16-bit, 32-bit, or 64-bit.

• Data bus, control bus and address bus are the types of system buses.

Data bus

·       It is the pathway through which data is transferred from one component to another.

·       It is one directional for I/O devices and bi-directional for memory and the CPU. allows for transferring data from RAM to the CPU and vice versa in both directions.

·       Allows for the transferring of data from input devices to the main memory and from the main memory to output devices in only one direction.

·       The wider data bus can transmit more data at a time.

·       It may be serial or parallel and can be of 32 bits, 64 bits or even more bits.

·       The serial data bus has one wire or path, and carries all the bits, one after the other.

·       The parallel data bus has many wires or pathways through which data are transferred simultaneously.

·       USB and SATA are the common serial data buses.

 

Control bus

• It carries the timing and control signals necessary to control and coordinate the activities of the entire computer system.

• It is bi-directional for the CPU and other components.

• It is used by the CPU to control, manage, and communicate with different components by transferring control signals (commands) to different components.

• It is used by other devices to transfer the status signals back to the CPU.

• It manages the information flow between components, indicating whether the operation is a read or a write and ensuring that the operation occurs at the right time.

 

Address bus

• It is the pathway used to transfer the addresses of memory or I/O devices where the next instruction to be executed or the next piece of data will be found.

• It carries a memory address and determines the location in memory that the processor will read data from or write data to.

• It is unidirectional from the CPU to all other components.

• The number of bits of address bus determines the maximum size of memory that the processor can access. The address bus of 16 bits can transfer a maximum 16-bit address, which means it can address 65,536 different memory locations.

 

 

1.2.5 PRIMARY MEMORY

• It is the part of the computer that stores data, information, instructions, or programs either temporarily or permanently.

• It is a semiconductor based internal memory.

• ROM and RAM are two types of primary memory.

• ROM, also called CMOS, contains the BIOS program (i.e., firmware) which can only be read by the CPU but cannot be erased or deleted.

ROM

• also called CMOS, contains the BIOS program (i.e., firmware) which

can only be read by the CPU but cannot be erased or deleted.

• PROM, EPROM and EEPROM are three types of ROM.

• PROM allows a programmer to write the program or data once on it.

• EPROM allows a programmer to rewrite the data or program on it by erasing the pervious contents.

• EEPROM allows a programmer to erase and reprogram repeatedly under the software control.

 

RAM

• is a semiconductor memory which is made up of several small storage areas called locations or cells.

• stores data, instructions, or programs temporarily. It is volatile in nature.

• SRAM and DRAM are two types of RAM.

• SRAM stores a bit of data if the electricity is provided to it.

• The contents of SRAM do not require refreshing periodically.

• DRAM stores data, instructions, or programs temporarily if the electricity is provided to it.

• It is required to be refreshed or recharged at the interval of time.

 

CACHE MEMORY

• It is a high-speed memory that is built into a CPU or on a separate chip and is placed in between the CPU and the main memory, whose access time is very close to the processing speed of the CPU.

• The cache built into the CPU is known as the Level 1 (L1) cache.

• The cache built on a separate chip is known as the Level 2 (L2) cache.

• The Level 2 cache acts as a buffer between the CPU and the main memory.

• The OS transfers data and program that are most frequently used by

the CPU to cache memory where microprocessor first checks the required data and instructions.

• It helps to reduce data accessing time and improves overall system speed.

Buffer

•It is an area of memory used for the temporary storage of data when a program or hardware device needs an uninterrupted flow of information.

•It enables the CPU to manipulate data before transferring it to a device.

•It helps to run a computer efficiently.

•Buffers are usually created in Random Access Memory (RAM) rather than other devices. Some hardware devices like printer, hard disk come with their own on-board RAM.

•Printers usually have smaller buffers which hold the data sent from the computer for printing and make free system RAM to handle other tasks. This allows print jobs to run in the background and is referred to as SPOOLING.

•Many programs like word processor, use a buffer to keep track of changes to files and updates the disk file with the contents of the buffer when the file is saved.

•While watching online videos, parts of the video files are download continuously and are stored on the buffer before beginning to play which makes the smooth video playing.

Virtual memory

•A computer has limited amount of main memory (RAM), which is broken up into smaller segments (i.e., pages).

•When many programs are running at one time, there may not be sufficient spaces (pages) in RAM to load a new program. So, the computer system uses some uses some spaces on a hard disk as a virtual memory.

•The computer system transfers data from RAM to virtual memory which are not currently used by the programs and makes free spaces in the RAM.

•Virtual memory is the temporary space on a hard disk which stores data of RAM which are not currently used by the programs.

•When the data in the virtual memory is required, the computer system moves other pages to the virtual memory and brings the required pages back to RAM. This process is known as paging or swapping and the temporary storage space on the hard disk is called a page file or a swap file.

 

1.2.6 SECONDARY MEMORY

• A device that stores data permanently.

• The CPU cannot access the data and programs on a secondary memory, so data and programs are required to transferred from it to RAM.

• Magnetic disk, flash memory, optical disk, external storage device and memo stick are the commonly used secondary memories.

Magnetic Disk

• The most popular direct access storage device that consists of a circular disc made of metal or plastic and is coated with magnetic material.

• The surface of a disk is divided into concentric circles called tracks and pie shaped blocks called sectors.

• The data is stored on the tracks of a disk surface in the form of invisible tiny magnetic spots. A positive magnetized spot represents a 1 bit, and the negative magnetized spot represents a 0 bit.

• Magnetic disks are reliable and durable storage devices. Hard disk, floppy disk, zip disk, super disk, Jaz disk, etc. are the magnetic disks.

• A hard disk is the most used secondary storage device that consists of one or more metal disks (called platters) coated with magnetic material where data are stored. The read/write head reads and write data. on the platters.

• Other magnetic disks except hard disk are not used nowadays.

Flash Memory

• is an electrically erasable programmable read-only memory (EEPROM).

• It is available as a USB memory stick (pen drive) and solid-state drive (SSD).

• When a pen drive is plugged into a computer's USB port, it behaves like an external disk drive. A pen drive is specially used for transferring data, songs, games, and programs from one computer to another.

• A solid-state drive (SSD) uses flash memory chips to store data and is comparatively faster and more reliable than a hard disk.

•  SSD has mainly two components: a flash controller and NAND flash memory chips.

 

Optical Disk

•A storage device that uses laser light technology to store and retrieve data.

•An optical disc is a circular disk made of rigid plastic or metal that is coated with highly reflecting material.

•While writing data, a high intensity laser beam is focused on the metal coated surface of the optical disk which forms tiny holes (or pits) on the metal coated surface of the disk along its tracks. A pit represents a value of 1 and a flat spot or land represents a value of 0.

•While reading, a low intensity laser beam is focused on the disk surface and the reflected laser is sensed by a photodiode (light sensitive semiconductor diode). The intensity of reflected laser beam from the pits is weak and is high from the flat spots. These high and low patterns of the reflected laser beam are sensed by photodiode and converted into electronic signals.

•The commonly used optical disks are Compact disk, Digital versatile disk, and Blu-ray disk. A CD can store 600-700 MB data. A DVD can store 4.7 GB to 17 GB data. A BD can store 25 GB to 100 GB data.

•A computer system needs optical disk drive to access the contents of an optical disk.

 

1.2.7 INPUT DEVICES

• A device through which data and instructions are entered into the computer system.

• converts the human understandable data and instructions into electronic signals that a computer understands and transfers to RAM.

• The data or instructions that are entered into a computer are known as input.

• Keyboard, mouse, scanner, light pen, optical magnetic reader (OMR), optical character reader (OCR), Bar code reader (BCR), magnetic ink character recognition (MICR), touch pad, Touch Screen, microphone, digital camera, joystick, etc., are input devices.

 

a. Keyboard

– An input device that contains alphabet keys, number keys, punctuation mark keys and some other characters keys.

– used for entering data like letters, text, numbers, symbols, and instructions to a computer.

– When a key is pressed, the keyboard encoder (electronic circuit) recognizes the pressed key and generates the related binary code and transmits it to the computer. For example, when you press an alphabet key ‘A’, a keyboard encoder generates binary code ‘01000001’.

 

b. Mouse

– A small handheld input device that allows a user to point and select items, icons or commands displayed on the graphical user interface (GUI) environment.

– consists of a plastic housing or casing with a flat bottom and two or three buttons on the top surface.

– A mouse may be a mechanical mouse or optical mouse.

 

c. Touch Pad

– A touch-sensitive pad which works like a mouse and is used on a laptop.

 

d. Light Pen

– A pen-shaped input device that has light-sensitive element on the tip of it and when it is placed

against the screen, it detects the light from the screen, enabling the computer to identify the location of the pen on the screen.

– It is used to draw pictures or select menu options onto the screen by directly pointing at the menus.

 

e. Scanner

– An input device that makes duplicate of any photo, handwritten or printed document in digital form into a computer.

– It works like a photocopy machine.

– Flat-bed scanners and handheld scanners are the most used scanners.

– A flatbed scanner has a sheet of glass over which a photo or printed text to be scanned is placed.

– A handheld scanner is a portable scanner that can be held in a user's hand and moved over the document to be scanned.

 

f. Optical Mark Reader (OMR)

– An input device that uses a light source to read marks and converts them into digital data that a

computer can process.

– It can read and count a pre-specified type of mark, such as small circles or rectangles made with a pencil or ball pen.

 

g. Optical Character Reader (OCR)

• An input device that uses a light source to read characters and converts them into digital data that a computer can process.

 

h. Magnetic Ink Character Reader (MICR)

• used in a bank to process a large volume of cheques and demand draffs.

• When a cheque is brought by a person to cash, the cheque is kept in the MICR, which reads the data and transfers the information to the CPU for immediate processing.

 

i. Bar Code Reader

• An input device that reads the Universal Product Code (UPC) of a bar code and transfers it to a computer.

• A bar code represents data in a set of vertical parallel lines of varying thicknesses with gaps.

• Books and goods in the market are labelled with bar codes.

 

j. Touch Screen

• A touch-sensitive electronic visual display screen which enables a user to input data or instructions just by selecting items displayed on a screen by using a stylus or finger.

• Touch screens are common in devices such as laptops, mobile phones, tablets, electronic voting machines, point of sale (POS) systems, ATMs, interactive multimedia boards, car GPS, kiosks, and token dispensers. Laptop with Touchscreen Laptop with Touchscreen Interactive Board Interactive Board

 

k. Digital Camera

– An input device which captures pictures and videos and stores them in a digital format in the memory chip.

– The photos stored in the digital camera can be viewed and erased immediately.

 

l. Microphone

– An input device used for entering audio, sound, or voice into a computer.

– It captures sound waves, converts them into digital format, and provides them to the CPU.

– The input sound or voice can be saved on a computer as a sound file.

 

1.2.8 OUTPUT DEVICES

• All the devices that are used to display or present the result of processing and other information to the user in a human understandable form are known as output devices.

• Monitor, printer, speaker, projector, and plotter are output devices.

• Output devices may be softcopy output devices or hardcopy output devices.

• The output displayed or presented by a softcopy output device is not permanent. A monitor, speaker, and projector are softcopy output devices.

• The output displayed or presented by a hardcopy output device is permanent. A printer and a plotter are the hardcopy output devices.

a. Monitor

• Also known as a visual/video display unit (VDU) or video display terminal (VDT).

• It displays data, information, or the result of processing on its screen.

• Softcopy output device.

• Monitors may be CRT monitor or LCD/LED monitor.

• A CRT monitor is based on a cathode ray tube.

• Both LCD and LED monitors use liquid crystal to form images.

• Fluorescent lamps or tubes that are used as the backlight in LCD monitor.

• Light-emitting diodes are used as the backlight in a LED monitor.

b. Speaker

• A softcopy output device that plays sound generated by the computer.

• A speaker is needed to connect to the soundcard of the computer.

 

c. Printer

• A hardcopy output device that displays the data or result of processing on paper.

• Printers may be non-impact printers or impact printers.

1.2.9 HARDWARE INTERFACES

a. Serial Port

·       A 9-pin serial communication interface port through which 1 bit of data can be transferred.

·       commonly used to connect a mouse and modem.

b. Parallel port

• A 25-pin connector/interface that connects an external device, such as printer, scanner, or Zip disk drive.

• Centronics port.

• It can transfer 8 bits of data simultaneously.

 

c. Universal serial bus (USB) Port

·       the most used interface in the computer system nowadays for connecting peripheral devices like keyboard, mouse, digital camera, printer, scanner, etc.

·       It can support a maximum of 127 external devices at a time on a computer.

d. Firewire

·       A high-speed serial bus for connecting high speed devices like audio/video equipment, aeronautical devices, medical equipment, etc.

·       It can transfer 400 MB of data per second.

·       It can support up to 63 external devices at a time on a single computer.

e. High-definition multimedia interface (HDMI) Port

·       A port used for connecting audio/video equipment.

·       A monitor, projector, digital camera, etc. can be connected through the HDMI ports.

f. Expansion Slots

·       A socket on the motherboard that allows an expansion card/daughter board to be connected.

·       A computer motherboard may have PCI Express, PCI (Peripheral Component Interconnect), AGP (Accelerated Graphics Port) or ISA (Industry Standard Architecture) slots.