Computer Organization and Architecture
UNIT- 1IntroductionQ1) Explain in detail Generations of computerA1) Generation in computer terminology is a change in technology a computer is/was being used. Initially, the generation term was used to distinguish between varying hardware technologies. Nowadays, generation includes both hardware and software, which together make up an entire computer system.There are five computer generations known till date. Each generation has been discussed in detail along with their time period and characteristics. In the following table, approximate dates against each generation have been mentioned, which are normally accepted.Following are the main five generations of computers.First GenerationThe period of first generation was from 1946-1959. The computers of first generation used vacuum tubes as the basic components for memory and circuitry for CPU (Central Processing Unit). These tubes, like electric bulbs, produced a lot of heat and the installations used to fuse frequently. Therefore, they were very expensive and only large organizations were able to afford it.In this generation, mainly batch processing operating system was used. Punch cards, paper tape, and magnetic tape was used as input and output devices. The computers in this generation used machine code as the programming language.
The main features of the first generation are −Vacuum tube technology Unreliable Supported machine language only Very costly Generated a lot of heat Slow input and output devices Huge size Need of AC Non-portable Consumed a lot of electricity Some computers of this generation were −ENIAC EDVAC UNIVAC IBM-701 IBM-650 Second GenerationThe period of second generation was from 1959-1965. In this generation, transistors were used that were cheaper, consumed less power, more compact in size, more reliable and faster than the first generation machines made of vacuum tubes. In this generation, magnetic cores were used as the primary memory and magnetic tape and magnetic disks as secondary storage devices.In this generation, assembly language and high-level programming languages like FORTRAN, COBOL were used. The computers used batch processing and multiprogramming operating system.
The main features of second generation are −Use of transistors Reliable in comparison to first generation computers Smaller size as compared to first generation computers Generated less heat as compared to first generation computers Consumed less electricity as compared to first generation computers Faster than first generation computers Still very costly AC required Supported machine and assembly languages Some computers of this generation were −IBM 1620 IBM 7094 CDC 1604 CDC 3600 UNIVAC 1108 Third GenerationThe period of third generation was from 1965-1971. The computers of third generation used Integrated Circuits (ICs) in place of transistors. A single IC has many transistors, resistors, and capacitors along with the associated circuitry.The IC was invented by Jack Kilby. This development made computers smaller in size, reliable, and efficient. In this generation remote processing, time-sharing, multiprogramming operating system were used. High-level languages (FORTRAN-II TO IV, COBOL, PASCAL PL/1, BASIC, ALGOL-68 etc.) were used during this generation.
The main features of third generation are −IC used More reliable in comparison to previous two generations Smaller size Generated less heat Faster Lesser maintenance Costly AC required Consumed lesser electricity Supported high-level language Some computers of this generation were −IBM-360 series Honeywell-6000 series PDP (Personal Data Processor) IBM-370/168 TDC-316 Fourth GenerationThe period of fourth generation was from 1971-1980. Computers of fourth generation used Very Large Scale Integrated (VLSI) circuits. VLSI circuits having about 5000 transistors and other circuit elements with their associated circuits on a single chip made it possible to have microcomputers of fourth generation.Fourth generation computers became more powerful, compact, reliable, and affordable. As a result, it gave rise to Personal Computer (PC) revolution. In this generation, time sharing, real time networks, distributed operating system were used. All the high-level languages like C, C++, DBASE etc., were used in this generation.The main features of fourth generation are −VLSI technology used Very cheap Portable and reliable Use of PCs Very small size Pipeline processing No AC required Concept of internet was introduced Great developments in the fields of networks Computers became easily available Some computers of this generation were −DEC 10 STAR 1000 PDP 11 CRAY-1(Super Computer) CRAY-X-MP(Super Computer) Fifth GenerationThe period of fifth generation is 1980-till date. In the fifth generation, VLSI technology became ULSI (Ultra Large Scale Integration) technology, resulting in the production of microprocessor chips having ten million electronic components.This generation is based on parallel processing hardware and AI (Artificial Intelligence) software. AI is an emerging branch in computer science, which interprets the means and method of making computers think like human beings. All the high-level languages like C and C++, Java, .Net etc., are used in this generation.
AI includes −Robotics Neural Networks Game Playing Development of expert systems to make decisions in real-life situations Natural language understanding and generation The main features of fifth generation are −ULSI technology Development of true artificial intelligence Development of Natural language processing Advancement in Parallel Processing Advancement in Superconductor technology More user-friendly interfaces with multimedia features Availability of very powerful and compact computers at cheaper rates Some computer types of this generation are −Desktop Laptop Notebook Ultrabook Chromebook Q2) What is Computer Block Diagram?A2) Mainly computer system consists of three parts that are central processing unit (CPU), Input Devices, and Output Devices. The Central Processing Unit (CPU) is divided into two parts again: arithmetic logic unit (ALU) and the control unit (CU). The set of instruction is in the form of raw data. A large amount of data is stored in the computer memory with the help of primary and secondary storage devices. The CPU is like the heart/brain of the computer. The user does not get the desired output, without the necessary option taken by the CPU. The Central processing unit (CPU) is responsible for the processing of all the instructions which are given by the user to the computer system.
Fig: Block Diagram of the computer. The data is entered through input devices such as the keyboard, mouse, etc. This set of instruction is processed by the CPU after getting the input by the user, and then the computer system produces the output. The computer can show the output with the help of output devices to the user, such as monitor, printer, etc.CPU (Central Processing Unit) Storage Unit ALU(Arithmetic Logic Unit) Control Unit Central Processing Unit (CPU)The computer system is nothing without the Central processing Unit so, it is also known as the brain or heat of computer. The CPU is an electronic hardware device which can perform different types of operations such as arithmetic and logical operation.
The CPU contains two parts: the arithmetic logic unit and control unit. We have discussed briefly the arithmetic unit, logical unit, and control unit which are given below:Control UnitThe control unit (CU) controls all the activities or operations which are performed inside the computer system. It receives instructions or information directly from the main memory of the computer. When the control unit receives an instruction set or information, it converts the instruction set to control signals then; these signals are sent to the central processor for further processing. The control unit understands which operation to execute, accurately, and in which order.Arithmetic and Logical UnitThe arithmetic and logical unit is the combinational digital electronic circuit that can perform arithmetic operations on integer binary numbers.It presents the arithmetic and logical operation. The outputs of ALU will change asynchronously in response to the input. The basic arithmetic and bitwise logic functions are supported by ALU.Storage UnitThe information or set of guidelines are stored in the storage unit of the computer system. The storage unit provides the space to store the data or instruction of processed data. The information or data is saved or hold in computer memory or storage device. The data storage is the core function and fundamental of the computer components. Q3) What are the Components of Computer System?A3) The hardware and software exist on the computer. The information which is stored through the device is known as computer software. The hardware components of the computer system are related to electronic and mechanical parts, and the software component is related to data and computer programs. Many elements are connected to the main circuit board of the computer system called a “motherboard.”
Processor. Main Memory. Secondary Memory. Input Devices. Output Devices. These are mainly five components of the computer system. The computer hardware, computer software, and liveware exist in the element of the computer system. ProcessorThe processor is an electric circuitry within the computer system. The Central processing unit is the central processor or main processor of the computer system. The processor carries out the instructions of the computer program with the help of basic arithmetic and logic, input/output operations.Main Memory The Random Access Memory is the main memory of the computer system, which is known as RAM. The main memory can store the operating system software, application software, and other information. The Ram is one of the fastest memory, and it allows the data to be readable and writeable.Secondary memory We can store the data and programs on a long-term basis in the secondary memory. The hard disks and the optical disks are the common secondary devices. It is slow and cheap memory as compare to primary memory. This memory is not connected to the processor directly. It has a large capacity to store the data. The hard disk has a capacity of 500 gigabytes. The data and programs on the hard disk are organized into files, and the file is the collection of data on the disk. The secondary storage is direct access by the CPU; that’s why it is different from the primary storage.The hard disk is about 100 times the capacity of the main memory. The main difference between primary and secondary storage is speed and capacity. There are several large blocks of data which are copied from the hard disk into the main memory. Input DevicesThe user provides the set of instruction or information to the computer system with the help of input devices such as the keyboard, mouse, scanner, etc. The data representation to the computer system is in the form of binary language after that the processor processes the converted data. The input unit implements the data which is instructed by the user to the system. We can enter the data from the outside world into the primary storage as the input through input devices. The input devices are the medium of communication between the outside world and the computer system. There are some important features of input devices which are given below:The input devices receive or accept the data or instruction from the user, who exist in the outside world. These devices convert the data or instruction into the machine-readable form for further processing. The input device performs like the connection between the outside world and our computer system. The keyboard and mouse are common examples of input devices. When the whole procedure is finished, we get the desired output from the output devices such as monitor, printer, etc. Output Devices The output devices produce or generate the desired result according to our input, such as a printer, monitor, etc. These devices convert the data into a human-readable form from binary code. The computer system is linked or connected to the outside world with the help of output devices. The primary examples of output devices are a printer, projector, etc. These devices have various features which are given below: These devices receive or accept the data in the binary form. The output devices convert the binary code into the human-readable form. These devices produce the converted result and show to the user. Q4) Explain Central Processing Unit (CPU)A4) What is a CPU in Computer System? :: The CPU stands for Central Processing Unit and additionally called a Microprocessor or Microchip. Now the CPU or microprocessor is the essential and fundamental part of computer system, where all the arithmetic and logical calculation takes place. It interprets, translates, and carries out the instructions for operating a computer as a device.In other words, the set of instructions or data are introduced to the PC system in form of raw data through input devices of computer, and later this instruction are processed or prepared to get desired or wanted result.
Central Processing Unit [Microprocessor]Now as we talk or discuss CPU’s or Microprocessor we tend to talk about their speed, accuracy, and reliability, as the significant computer technology development the speed of CPU’s has changed dramatically. Most processors nowadays are multicore processors. A multi-core processor is a single chip with at least two or more separate processor core, or layers which has the circuitry to process instructions and directions.Every PC contains no less than one processor yet you can see many computers with multiple processors, this processor executes each instruction and directions separately.The processor or CPU are installed on motherboard or mainboard they are typically square shaped with more than 250 pins on the base surface of the chip, the processor is connected or associated with the motherboard by a Zero insertion force (ZIF).To avoid from overheating heat sink and CPU fan is installed on processors. Common multicore processor are :: Dual- Core Processor is a processor which contains two separate cores of processors Triple core processor contains three separate cores of processors Quad-Core processor contains four separate cores of processors The CPU is also considered as a brain of computer Famous manufacturers of processor are Intel and AMD Components of CPU [Central Processing Unit ]The main or fundamental component of CPUs are Arithmetic logic unit, Control unit and Cache Memory.
Arithmetic and logic unit ::
ALU perform all the arithmetic and logic calculation provided to computer systems that are addition,substraction,multiplication,division,comparison,greater,less.
Control Unit ::
This unit controls and facilitates all the activities and operations performed in the PC system. It gets programs from the main memory of the computer system to interpret or translate them and control other units to get the desired result.
Cache ::
Cache memory dwells between the main memory and processor. The rate of exchanging data and information is substantially higher compared to other memory of computer system. The cache memory saves and holds the data or set of information that is about to process immediately by the system.
The cache memory is not available to users they cannot delete, update, refresh the programs inside the memory, the manufacturer, or the computer programmers can erase or update the data which is stored inside the cache memory.
They are quite expensive therefore they were first introduced or installed in a large computer only in small numbers however as the technology developed the small computer, or desktop computer used cache memory and we usually call them as l1 cache and l2 cache. CPU [Central Processing Unit] | Processor SpeedThe speed of the microprocessor is the essential ingredient as the software technology has developed to the extreme use of large programs and application are made available to users to execute this application high speed of processors are required. The processor speed can be defined and characterized as the speed at which it executes the instructions and directions. The speed of the processor is measured in MHz (Millions of Pulses for each second) and GHz (Billion of pulses for each second)The speed of mini and mainframe computers are measured in MIPS (Millions of instruction per second) and BIPS (Billions of instructions per second). Functions of CPU in ComputerThe CPU Is considered as the brain or heart of the computer as it is responsible for each and every operation performed in a computer system. It controls and organizes every section and unit of a Personal computer. Every instruction passed to a computer system is firstly converted into binary numbers that consist of 0s 1s which is in machine-readable form later this instruction which has been changed over are send to the registry and eventually they are transferred and exchanged to CPU for further and additional processing and preparing as processor have ALU which stands for Arithmetic and logical operation with the help of ALU computer performs every mathematical and logical operation.There are Four Primary Functions of ProcessorFetch Decode Execute Store Fetch :: Every instruction and data is stored in memory with a specific address. The processor gets the address number from program counter this is done for executing next instruction quickly.
Decode:: All the program or instruction are translated from assembly language or low level to binary language which helps the computer system to deliver the output in human-readable or intelligent form. This process of conversion and transformation from one language to another is called as DECODING
Execute :: The processor recovers the instructions and data from memory and processes them to get wanted output with the assistance of ALU (Arithmetic and coherent unit).
Store :: After the procedure is finished in ALU. The output is put away in memory for additionally processing. The speed of PC altogether relies on the CPU. The fundamental usefulness of PC can be made fast by introducing present-day processors. Q5) What is VDU?A5) Stands for "Visual Display Unit." A VDU displays images generated by a computer or other electronic device. The term VDU is often used synonymously with "monitor," but it can also refer to another type of display, such as a digital projector. Visual display units may be peripheral devices or may be integrated with the other components. For example, the Apple iMac uses an all-in-one design, in which the screen and computer are built into a single unit.Early VDUs were primarily cathode ray tube (CRT) displays and typically had a diagonal size of 13 inches or less. During the 1990s, 15" and 17" displays became standard, and some manufacturers began producing displays over 20" in size. At the turn of the century, flat panel displays became more common, and by 2006, CRT displays were hard to find.Today, it is common for computers to come with VDUs that are 20" to 30" in size. Thanks to the recent growth in LCD, plasma, and LED technology, manufacturing large screens is much more cost effective than before. Q6) Explain Keyboard and MouseA6) KeyboardKeyboard 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.
Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet.The keys on the keyboard are as follows −
MouseMouse 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.
AdvantagesEasy to use Not very expensive Moves the cursor faster than the arrow keys of the keyboard. Q7) Explain different Input DevicesA7) 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 Magnetic Ink Card Reader(MICR) Optical Character Reader(OCR) Bar Code Reader Optical Mark Reader(OMR) KeyboardKeyboard 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.
Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet.The keys on the keyboard are as follows −
MouseMouse 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.
AdvantagesEasy to use Not very expensive Moves the cursor faster than the arrow keys of the keyboard. JoystickJoystick 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.Light PenLight 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.Track BallTrack 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.ScannerScanner 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.DigitizerDigitizer 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.MicrophoneMicrophone is an input device to input sound that is then stored in a digital form.
The microphone is used for various applications such as adding sound to a multimedia presentation or for mixing music.Magnetic Ink Card Reader (MICR)MICR input device is generally used in banks as there are large number of cheques to be processed every day. The bank's code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable.
This reading process is called Magnetic Ink Character Recognition (MICR). The main advantages of MICR is that it is fast and less error prone.Optical Character Reader (OCR)OCR is an input device used to read a printed text.
OCR scans the text optically, character by character, converts them into a machine readable code, and stores the text on the system memory.Bar Code ReadersBar 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.Optical Mark Reader (OMR)OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked.
It is specially used for checking the answer sheets of examinations having multiple choice questions. Q8) Explain different Output DevicesA8) Following are some of the important output devices used in a computer.Monitors Graphic Plotter Printer MonitorsMonitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.There are two kinds of viewing screen used for monitors.Cathode-Ray Tube (CRT) Flat-Panel Display Cathode-Ray Tube (CRT) MonitorThe 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.A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.There are some disadvantages of CRT −Large in Size High power consumption Flat-Panel Display MonitorThe 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.
The flat-panel display is divided into two categories −Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes). Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device). PrintersPrinter is an output device, which is used to print information on paper.There are two types of printers −Impact Printers Non-Impact Printers Impact PrintersImpact 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 −Character printers Line printers Character PrintersCharacter 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 PrinterIn 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. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form a character which is why it is called Dot Matrix Printer.
AdvantagesInexpensive Widely Used Other language characters can be printed DisadvantagesSlow Speed Poor Quality Daisy WheelHead 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.
AdvantagesMore reliable than DMP Better quality Fonts of character can be easily changed DisadvantagesSlower than DMP Noisy More expensive than DMP Line PrintersLine printers are the printers which print one line at a time.
These are of two types −Drum Printer Chain Printer Drum PrinterThis printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute.AdvantagesVery high speed DisadvantagesVery expensive Characters fonts cannot be changed Chain PrinterIn this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.AdvantagesCharacter fonts can easily be changed. Different languages can be used with the same printer. DisadvantagesNoisy Non-impact PrintersNon-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 PrintersFaster than impact printers They are not noisy High quality Supports many fonts and different character size Laser PrintersThese are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.
AdvantagesVery high speed Very high quality output Good graphics quality Supports many fonts and different character size DisadvantagesExpensive Cannot be used to produce multiple copies of a document in a single printing Inkjet PrintersInkjet 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.AdvantagesHigh quality printing More reliable DisadvantagesExpensive as the cost per page is high Slow as compared to laser printer Q9) Explain Computer MemoryA9) A memory is just like a human brain. It is used to store data and instructions. Computer memory is the storage space in the computer, where data is to be processed and instructions required for processing are stored. The memory is divided into large number of small parts called cells. Each location or cell has a unique address, which varies from zero to memory size minus one. For example, if the computer has 64k words, then this memory unit has 64 * 1024 = 65536 memory locations. The address of these locations varies from 0 to 65535.Memory is primarily of three types −Cache Memory Primary Memory/Main Memory Secondary Memory Cache MemoryCache memory is a very high speed semiconductor memory which can speed up the CPU. It acts as a buffer between the CPU and the main memory. It is used to hold those parts of data and program which are most frequently used by the CPU. The parts of data and programs are transferred from the disk to cache memory by the operating system, from where the CPU can access them.
AdvantagesThe advantages of cache memory are as follows −Cache memory is faster than main memory. It consumes less access time as compared to main memory. It stores the program that can be executed within a short period of time. It stores data for temporary use. DisadvantagesThe disadvantages of cache memory are as follows −Cache memory has limited capacity. It is very expensive. 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 generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed resides in the main memory. It is divided into two subcategories RAM and ROM.
Characteristics of Main MemoryThese are semiconductor memories. It is known as the main memory. Usually volatile memory. Data is lost in case power is switched off. It is the working memory of the computer. Faster than secondary memories. A computer cannot run without the primary memory. Secondary MemoryThis 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. CPU directly does not access these memories, instead they are accessed via input-output routines. The contents of secondary memories are first transferred to the main memory, and then the CPU can access it. For example, disk, CD-ROM, DVD, etc.
Characteristics of Secondary MemoryThese 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. Q10) Explain Secondary storageQ10) You know that processor memory, also known as primary memory, is expensive as well as limited. The faster primary memories are also volatile. If we need to store large amount of data or programs permanently, we need a cheaper and permanent memory. Such memory is called secondary memory. Here we will discuss secondary memory devices that can be used to store large amount of data, audio, video and multimedia files.Characteristics of Secondary MemoryThese are some characteristics of secondary memory, which distinguish it from primary memory −It is non-volatile, i.e. it retains data when power is switched off It is large capacities to the tune of terabytes It is cheaper as compared to primary memory Depending on whether secondary memory device is part of CPU or not, there are two types of secondary memory – fixed and removable.
Let us look at some of the secondary memory devices available.Hard Disk DriveHard disk drive is made up of a series of circular disks called platters arranged one over the other almost ½ inches apart around a spindle. Disks are made of non-magnetic material like aluminum alloy and coated with 10-20 nm of magnetic material.
Standard diameter of these disks is 14 inches and they rotate with speeds varying from 4200 rpm (rotations per minute) for personal computers to 15000 rpm for servers. Data is stored by magnetizing or demagnetizing the magnetic coating. A magnetic reader arm is used to read data from and write data to the disks. A typical modern HDD has capacity in terabytes (TB).CD DriveCD stands for Compact Disk. CDs are circular disks that use optical rays, usually lasers, to read and write data. They are very cheap as you can get 700 MB of storage space for less than a dollar. CDs are inserted in CD drives built into CPU cabinet. They are portable as you can eject the drive, remove the CD and carry it with you. There are three types of CDs −CD-ROM (Compact Disk – Read Only Memory) − The data on these CDs are recorded by the manufacturer. Proprietary Software, audio or video are released on CD-ROMs. CD-R (Compact Disk – Recordable) − Data can be written by the user once on the CD-R. It cannot be deleted or modified later. CD-RW (Compact Disk – Rewritable) − Data can be written and deleted on these optical disks again and again. DVD DriveDVD stands for Digital Video Display. DVD are optical devices that can store 15 times the data held by CDs. They are usually used to store rich multimedia files that need high storage capacity. DVDs also come in three varieties – read only, recordable and rewritable.
Pen DrivePen drive is a portable memory device that uses solid state memory rather than magnetic fields or lasers to record data. It uses a technology similar to RAM, except that it is nonvolatile. It is also called USB drive, key drive or flash memory.
Blue Ray DiskBlue Ray Disk (BD) is an optical storage media used to store high definition (HD) video and other multimedia filed. BD uses shorter wavelength laser as compared to CD/DVD. This enables writing arm to focus more tightly on the disk and hence pack in more data. BDs can store up to 128 GB data.
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Arithmetic and logic unit ::
ALU perform all the arithmetic and logic calculation provided to computer systems that are addition,substraction,multiplication,division,comparison,greater,less.
Control Unit ::
This unit controls and facilitates all the activities and operations performed in the PC system. It gets programs from the main memory of the computer system to interpret or translate them and control other units to get the desired result.
Cache ::
Cache memory dwells between the main memory and processor. The rate of exchanging data and information is substantially higher compared to other memory of computer system. The cache memory saves and holds the data or set of information that is about to process immediately by the system.
The cache memory is not available to users they cannot delete, update, refresh the programs inside the memory, the manufacturer, or the computer programmers can erase or update the data which is stored inside the cache memory.
They are quite expensive therefore they were first introduced or installed in a large computer only in small numbers however as the technology developed the small computer, or desktop computer used cache memory and we usually call them as l1 cache and l2 cache. CPU [Central Processing Unit] | Processor SpeedThe speed of the microprocessor is the essential ingredient as the software technology has developed to the extreme use of large programs and application are made available to users to execute this application high speed of processors are required. The processor speed can be defined and characterized as the speed at which it executes the instructions and directions. The speed of the processor is measured in MHz (Millions of Pulses for each second) and GHz (Billion of pulses for each second)The speed of mini and mainframe computers are measured in MIPS (Millions of instruction per second) and BIPS (Billions of instructions per second). Functions of CPU in ComputerThe CPU Is considered as the brain or heart of the computer as it is responsible for each and every operation performed in a computer system. It controls and organizes every section and unit of a Personal computer. Every instruction passed to a computer system is firstly converted into binary numbers that consist of 0s 1s which is in machine-readable form later this instruction which has been changed over are send to the registry and eventually they are transferred and exchanged to CPU for further and additional processing and preparing as processor have ALU which stands for Arithmetic and logical operation with the help of ALU computer performs every mathematical and logical operation.There are Four Primary Functions of Processor
Decode:: All the program or instruction are translated from assembly language or low level to binary language which helps the computer system to deliver the output in human-readable or intelligent form. This process of conversion and transformation from one language to another is called as DECODING
Execute :: The processor recovers the instructions and data from memory and processes them to get wanted output with the assistance of ALU (Arithmetic and coherent unit).
Store :: After the procedure is finished in ALU. The output is put away in memory for additionally processing. The speed of PC altogether relies on the CPU. The fundamental usefulness of PC can be made fast by introducing present-day processors. Q5) What is VDU?A5) Stands for "Visual Display Unit." A VDU displays images generated by a computer or other electronic device. The term VDU is often used synonymously with "monitor," but it can also refer to another type of display, such as a digital projector. Visual display units may be peripheral devices or may be integrated with the other components. For example, the Apple iMac uses an all-in-one design, in which the screen and computer are built into a single unit.Early VDUs were primarily cathode ray tube (CRT) displays and typically had a diagonal size of 13 inches or less. During the 1990s, 15" and 17" displays became standard, and some manufacturers began producing displays over 20" in size. At the turn of the century, flat panel displays became more common, and by 2006, CRT displays were hard to find.Today, it is common for computers to come with VDUs that are 20" to 30" in size. Thanks to the recent growth in LCD, plasma, and LED technology, manufacturing large screens is much more cost effective than before. Q6) Explain Keyboard and MouseA6) KeyboardKeyboard 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.
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S.No | Keys & Description |
1 | Typing Keys 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 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. |
3 | Function Keys 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. |
4 | Control keys 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). |
5 | Special Purpose Keys Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen. |
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S.No | Keys & Description |
1 | Typing Keys 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 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. |
3 | Function Keys 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. |
4 | Control keys 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). |
5 | Special Purpose Keys Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen. |
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UNIT- 1IntroductionQ1) Explain in detail Generations of computerA1) Generation in computer terminology is a change in technology a computer is/was being used. Initially, the generation term was used to distinguish between varying hardware technologies. Nowadays, generation includes both hardware and software, which together make up an entire computer system.There are five computer generations known till date. Each generation has been discussed in detail along with their time period and characteristics. In the following table, approximate dates against each generation have been mentioned, which are normally accepted.Following are the main five generations of computers.First GenerationThe period of first generation was from 1946-1959. The computers of first generation used vacuum tubes as the basic components for memory and circuitry for CPU (Central Processing Unit). These tubes, like electric bulbs, produced a lot of heat and the installations used to fuse frequently. Therefore, they were very expensive and only large organizations were able to afford it.In this generation, mainly batch processing operating system was used. Punch cards, paper tape, and magnetic tape was used as input and output devices. The computers in this generation used machine code as the programming language.
The main features of the first generation are −Vacuum tube technology Unreliable Supported machine language only Very costly Generated a lot of heat Slow input and output devices Huge size Need of AC Non-portable Consumed a lot of electricity Some computers of this generation were −ENIAC EDVAC UNIVAC IBM-701 IBM-650 Second GenerationThe period of second generation was from 1959-1965. In this generation, transistors were used that were cheaper, consumed less power, more compact in size, more reliable and faster than the first generation machines made of vacuum tubes. In this generation, magnetic cores were used as the primary memory and magnetic tape and magnetic disks as secondary storage devices.In this generation, assembly language and high-level programming languages like FORTRAN, COBOL were used. The computers used batch processing and multiprogramming operating system.
The main features of second generation are −Use of transistors Reliable in comparison to first generation computers Smaller size as compared to first generation computers Generated less heat as compared to first generation computers Consumed less electricity as compared to first generation computers Faster than first generation computers Still very costly AC required Supported machine and assembly languages Some computers of this generation were −IBM 1620 IBM 7094 CDC 1604 CDC 3600 UNIVAC 1108 Third GenerationThe period of third generation was from 1965-1971. The computers of third generation used Integrated Circuits (ICs) in place of transistors. A single IC has many transistors, resistors, and capacitors along with the associated circuitry.The IC was invented by Jack Kilby. This development made computers smaller in size, reliable, and efficient. In this generation remote processing, time-sharing, multiprogramming operating system were used. High-level languages (FORTRAN-II TO IV, COBOL, PASCAL PL/1, BASIC, ALGOL-68 etc.) were used during this generation.
The main features of third generation are −IC used More reliable in comparison to previous two generations Smaller size Generated less heat Faster Lesser maintenance Costly AC required Consumed lesser electricity Supported high-level language Some computers of this generation were −IBM-360 series Honeywell-6000 series PDP (Personal Data Processor) IBM-370/168 TDC-316 Fourth GenerationThe period of fourth generation was from 1971-1980. Computers of fourth generation used Very Large Scale Integrated (VLSI) circuits. VLSI circuits having about 5000 transistors and other circuit elements with their associated circuits on a single chip made it possible to have microcomputers of fourth generation.Fourth generation computers became more powerful, compact, reliable, and affordable. As a result, it gave rise to Personal Computer (PC) revolution. In this generation, time sharing, real time networks, distributed operating system were used. All the high-level languages like C, C++, DBASE etc., were used in this generation.The main features of fourth generation are −VLSI technology used Very cheap Portable and reliable Use of PCs Very small size Pipeline processing No AC required Concept of internet was introduced Great developments in the fields of networks Computers became easily available Some computers of this generation were −DEC 10 STAR 1000 PDP 11 CRAY-1(Super Computer) CRAY-X-MP(Super Computer) Fifth GenerationThe period of fifth generation is 1980-till date. In the fifth generation, VLSI technology became ULSI (Ultra Large Scale Integration) technology, resulting in the production of microprocessor chips having ten million electronic components.This generation is based on parallel processing hardware and AI (Artificial Intelligence) software. AI is an emerging branch in computer science, which interprets the means and method of making computers think like human beings. All the high-level languages like C and C++, Java, .Net etc., are used in this generation.
AI includes −Robotics Neural Networks Game Playing Development of expert systems to make decisions in real-life situations Natural language understanding and generation The main features of fifth generation are −ULSI technology Development of true artificial intelligence Development of Natural language processing Advancement in Parallel Processing Advancement in Superconductor technology More user-friendly interfaces with multimedia features Availability of very powerful and compact computers at cheaper rates Some computer types of this generation are −Desktop Laptop Notebook Ultrabook Chromebook Q2) What is Computer Block Diagram?A2) Mainly computer system consists of three parts that are central processing unit (CPU), Input Devices, and Output Devices. The Central Processing Unit (CPU) is divided into two parts again: arithmetic logic unit (ALU) and the control unit (CU). The set of instruction is in the form of raw data. A large amount of data is stored in the computer memory with the help of primary and secondary storage devices. The CPU is like the heart/brain of the computer. The user does not get the desired output, without the necessary option taken by the CPU. The Central processing unit (CPU) is responsible for the processing of all the instructions which are given by the user to the computer system.
Fig: Block Diagram of the computer. The data is entered through input devices such as the keyboard, mouse, etc. This set of instruction is processed by the CPU after getting the input by the user, and then the computer system produces the output. The computer can show the output with the help of output devices to the user, such as monitor, printer, etc.CPU (Central Processing Unit) Storage Unit ALU(Arithmetic Logic Unit) Control Unit Central Processing Unit (CPU)The computer system is nothing without the Central processing Unit so, it is also known as the brain or heat of computer. The CPU is an electronic hardware device which can perform different types of operations such as arithmetic and logical operation.
The CPU contains two parts: the arithmetic logic unit and control unit. We have discussed briefly the arithmetic unit, logical unit, and control unit which are given below:Control UnitThe control unit (CU) controls all the activities or operations which are performed inside the computer system. It receives instructions or information directly from the main memory of the computer. When the control unit receives an instruction set or information, it converts the instruction set to control signals then; these signals are sent to the central processor for further processing. The control unit understands which operation to execute, accurately, and in which order.Arithmetic and Logical UnitThe arithmetic and logical unit is the combinational digital electronic circuit that can perform arithmetic operations on integer binary numbers.It presents the arithmetic and logical operation. The outputs of ALU will change asynchronously in response to the input. The basic arithmetic and bitwise logic functions are supported by ALU.Storage UnitThe information or set of guidelines are stored in the storage unit of the computer system. The storage unit provides the space to store the data or instruction of processed data. The information or data is saved or hold in computer memory or storage device. The data storage is the core function and fundamental of the computer components. Q3) What are the Components of Computer System?A3) The hardware and software exist on the computer. The information which is stored through the device is known as computer software. The hardware components of the computer system are related to electronic and mechanical parts, and the software component is related to data and computer programs. Many elements are connected to the main circuit board of the computer system called a “motherboard.”
Processor. Main Memory. Secondary Memory. Input Devices. Output Devices. These are mainly five components of the computer system. The computer hardware, computer software, and liveware exist in the element of the computer system. ProcessorThe processor is an electric circuitry within the computer system. The Central processing unit is the central processor or main processor of the computer system. The processor carries out the instructions of the computer program with the help of basic arithmetic and logic, input/output operations.Main Memory The Random Access Memory is the main memory of the computer system, which is known as RAM. The main memory can store the operating system software, application software, and other information. The Ram is one of the fastest memory, and it allows the data to be readable and writeable.Secondary memory We can store the data and programs on a long-term basis in the secondary memory. The hard disks and the optical disks are the common secondary devices. It is slow and cheap memory as compare to primary memory. This memory is not connected to the processor directly. It has a large capacity to store the data. The hard disk has a capacity of 500 gigabytes. The data and programs on the hard disk are organized into files, and the file is the collection of data on the disk. The secondary storage is direct access by the CPU; that’s why it is different from the primary storage.The hard disk is about 100 times the capacity of the main memory. The main difference between primary and secondary storage is speed and capacity. There are several large blocks of data which are copied from the hard disk into the main memory. Input DevicesThe user provides the set of instruction or information to the computer system with the help of input devices such as the keyboard, mouse, scanner, etc. The data representation to the computer system is in the form of binary language after that the processor processes the converted data. The input unit implements the data which is instructed by the user to the system. We can enter the data from the outside world into the primary storage as the input through input devices. The input devices are the medium of communication between the outside world and the computer system. There are some important features of input devices which are given below:The input devices receive or accept the data or instruction from the user, who exist in the outside world. These devices convert the data or instruction into the machine-readable form for further processing. The input device performs like the connection between the outside world and our computer system. The keyboard and mouse are common examples of input devices. When the whole procedure is finished, we get the desired output from the output devices such as monitor, printer, etc. Output Devices The output devices produce or generate the desired result according to our input, such as a printer, monitor, etc. These devices convert the data into a human-readable form from binary code. The computer system is linked or connected to the outside world with the help of output devices. The primary examples of output devices are a printer, projector, etc. These devices have various features which are given below: These devices receive or accept the data in the binary form. The output devices convert the binary code into the human-readable form. These devices produce the converted result and show to the user. Q4) Explain Central Processing Unit (CPU)A4) What is a CPU in Computer System? :: The CPU stands for Central Processing Unit and additionally called a Microprocessor or Microchip. Now the CPU or microprocessor is the essential and fundamental part of computer system, where all the arithmetic and logical calculation takes place. It interprets, translates, and carries out the instructions for operating a computer as a device.In other words, the set of instructions or data are introduced to the PC system in form of raw data through input devices of computer, and later this instruction are processed or prepared to get desired or wanted result.
Central Processing Unit [Microprocessor]Now as we talk or discuss CPU’s or Microprocessor we tend to talk about their speed, accuracy, and reliability, as the significant computer technology development the speed of CPU’s has changed dramatically. Most processors nowadays are multicore processors. A multi-core processor is a single chip with at least two or more separate processor core, or layers which has the circuitry to process instructions and directions.Every PC contains no less than one processor yet you can see many computers with multiple processors, this processor executes each instruction and directions separately.The processor or CPU are installed on motherboard or mainboard they are typically square shaped with more than 250 pins on the base surface of the chip, the processor is connected or associated with the motherboard by a Zero insertion force (ZIF).To avoid from overheating heat sink and CPU fan is installed on processors. Common multicore processor are :: Dual- Core Processor is a processor which contains two separate cores of processors Triple core processor contains three separate cores of processors Quad-Core processor contains four separate cores of processors The CPU is also considered as a brain of computer Famous manufacturers of processor are Intel and AMD Components of CPU [Central Processing Unit ]The main or fundamental component of CPUs are Arithmetic logic unit, Control unit and Cache Memory.
Arithmetic and logic unit ::
ALU perform all the arithmetic and logic calculation provided to computer systems that are addition,substraction,multiplication,division,comparison,greater,less.
Control Unit ::
This unit controls and facilitates all the activities and operations performed in the PC system. It gets programs from the main memory of the computer system to interpret or translate them and control other units to get the desired result.
Cache ::
Cache memory dwells between the main memory and processor. The rate of exchanging data and information is substantially higher compared to other memory of computer system. The cache memory saves and holds the data or set of information that is about to process immediately by the system.
The cache memory is not available to users they cannot delete, update, refresh the programs inside the memory, the manufacturer, or the computer programmers can erase or update the data which is stored inside the cache memory.
They are quite expensive therefore they were first introduced or installed in a large computer only in small numbers however as the technology developed the small computer, or desktop computer used cache memory and we usually call them as l1 cache and l2 cache. CPU [Central Processing Unit] | Processor SpeedThe speed of the microprocessor is the essential ingredient as the software technology has developed to the extreme use of large programs and application are made available to users to execute this application high speed of processors are required. The processor speed can be defined and characterized as the speed at which it executes the instructions and directions. The speed of the processor is measured in MHz (Millions of Pulses for each second) and GHz (Billion of pulses for each second)The speed of mini and mainframe computers are measured in MIPS (Millions of instruction per second) and BIPS (Billions of instructions per second). Functions of CPU in ComputerThe CPU Is considered as the brain or heart of the computer as it is responsible for each and every operation performed in a computer system. It controls and organizes every section and unit of a Personal computer. Every instruction passed to a computer system is firstly converted into binary numbers that consist of 0s 1s which is in machine-readable form later this instruction which has been changed over are send to the registry and eventually they are transferred and exchanged to CPU for further and additional processing and preparing as processor have ALU which stands for Arithmetic and logical operation with the help of ALU computer performs every mathematical and logical operation.There are Four Primary Functions of ProcessorFetch Decode Execute Store Fetch :: Every instruction and data is stored in memory with a specific address. The processor gets the address number from program counter this is done for executing next instruction quickly.
Decode:: All the program or instruction are translated from assembly language or low level to binary language which helps the computer system to deliver the output in human-readable or intelligent form. This process of conversion and transformation from one language to another is called as DECODING
Execute :: The processor recovers the instructions and data from memory and processes them to get wanted output with the assistance of ALU (Arithmetic and coherent unit).
Store :: After the procedure is finished in ALU. The output is put away in memory for additionally processing. The speed of PC altogether relies on the CPU. The fundamental usefulness of PC can be made fast by introducing present-day processors. Q5) What is VDU?A5) Stands for "Visual Display Unit." A VDU displays images generated by a computer or other electronic device. The term VDU is often used synonymously with "monitor," but it can also refer to another type of display, such as a digital projector. Visual display units may be peripheral devices or may be integrated with the other components. For example, the Apple iMac uses an all-in-one design, in which the screen and computer are built into a single unit.Early VDUs were primarily cathode ray tube (CRT) displays and typically had a diagonal size of 13 inches or less. During the 1990s, 15" and 17" displays became standard, and some manufacturers began producing displays over 20" in size. At the turn of the century, flat panel displays became more common, and by 2006, CRT displays were hard to find.Today, it is common for computers to come with VDUs that are 20" to 30" in size. Thanks to the recent growth in LCD, plasma, and LED technology, manufacturing large screens is much more cost effective than before. Q6) Explain Keyboard and MouseA6) KeyboardKeyboard 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.
Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet.The keys on the keyboard are as follows −
MouseMouse 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.
AdvantagesEasy to use Not very expensive Moves the cursor faster than the arrow keys of the keyboard. Q7) Explain different Input DevicesA7) 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 Magnetic Ink Card Reader(MICR) Optical Character Reader(OCR) Bar Code Reader Optical Mark Reader(OMR) KeyboardKeyboard 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.
Keyboards are of two sizes 84 keys or 101/102 keys, but now keyboards with 104 keys or 108 keys are also available for Windows and Internet.The keys on the keyboard are as follows −
MouseMouse 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.
AdvantagesEasy to use Not very expensive Moves the cursor faster than the arrow keys of the keyboard. JoystickJoystick 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.Light PenLight 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.Track BallTrack 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.ScannerScanner 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.DigitizerDigitizer 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.MicrophoneMicrophone is an input device to input sound that is then stored in a digital form.
The microphone is used for various applications such as adding sound to a multimedia presentation or for mixing music.Magnetic Ink Card Reader (MICR)MICR input device is generally used in banks as there are large number of cheques to be processed every day. The bank's code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable.
This reading process is called Magnetic Ink Character Recognition (MICR). The main advantages of MICR is that it is fast and less error prone.Optical Character Reader (OCR)OCR is an input device used to read a printed text.
OCR scans the text optically, character by character, converts them into a machine readable code, and stores the text on the system memory.Bar Code ReadersBar 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.Optical Mark Reader (OMR)OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked.
It is specially used for checking the answer sheets of examinations having multiple choice questions. Q8) Explain different Output DevicesA8) Following are some of the important output devices used in a computer.Monitors Graphic Plotter Printer MonitorsMonitors, commonly called as Visual Display Unit (VDU), are the main output device of a computer. It forms images from tiny dots, called pixels that are arranged in a rectangular form. The sharpness of the image depends upon the number of pixels.There are two kinds of viewing screen used for monitors.Cathode-Ray Tube (CRT) Flat-Panel Display Cathode-Ray Tube (CRT) MonitorThe 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.A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.There are some disadvantages of CRT −Large in Size High power consumption Flat-Panel Display MonitorThe 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.
The flat-panel display is divided into two categories −Emissive Displays − Emissive displays are devices that convert electrical energy into light. For example, plasma panel and LED (Light-Emitting Diodes). Non-Emissive Displays − Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. For example, LCD (Liquid-Crystal Device). PrintersPrinter is an output device, which is used to print information on paper.There are two types of printers −Impact Printers Non-Impact Printers Impact PrintersImpact 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 −Character printers Line printers Character PrintersCharacter 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 PrinterIn 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. Each character printed is in the form of pattern of dots and head consists of a Matrix of Pins of size (5*7, 7*9, 9*7 or 9*9) which come out to form a character which is why it is called Dot Matrix Printer.
AdvantagesInexpensive Widely Used Other language characters can be printed DisadvantagesSlow Speed Poor Quality Daisy WheelHead 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.
AdvantagesMore reliable than DMP Better quality Fonts of character can be easily changed DisadvantagesSlower than DMP Noisy More expensive than DMP Line PrintersLine printers are the printers which print one line at a time.
These are of two types −Drum Printer Chain Printer Drum PrinterThis printer is like a drum in shape hence it is called drum printer. The surface of the drum is divided into a number of tracks. Total tracks are equal to the size of the paper, i.e. for a paper width of 132 characters, drum will have 132 tracks. A character set is embossed on the track. Different character sets available in the market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum printers are fast in speed and can print 300 to 2000 lines per minute.AdvantagesVery high speed DisadvantagesVery expensive Characters fonts cannot be changed Chain PrinterIn this printer, a chain of character sets is used, hence it is called Chain Printer. A standard character set may have 48, 64, or 96 characters.AdvantagesCharacter fonts can easily be changed. Different languages can be used with the same printer. DisadvantagesNoisy Non-impact PrintersNon-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 PrintersFaster than impact printers They are not noisy High quality Supports many fonts and different character size Laser PrintersThese are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page.
AdvantagesVery high speed Very high quality output Good graphics quality Supports many fonts and different character size DisadvantagesExpensive Cannot be used to produce multiple copies of a document in a single printing Inkjet PrintersInkjet 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.AdvantagesHigh quality printing More reliable DisadvantagesExpensive as the cost per page is high Slow as compared to laser printer Q9) Explain Computer MemoryA9) A memory is just like a human brain. It is used to store data and instructions. Computer memory is the storage space in the computer, where data is to be processed and instructions required for processing are stored. The memory is divided into large number of small parts called cells. Each location or cell has a unique address, which varies from zero to memory size minus one. For example, if the computer has 64k words, then this memory unit has 64 * 1024 = 65536 memory locations. The address of these locations varies from 0 to 65535.Memory is primarily of three types −Cache Memory Primary Memory/Main Memory Secondary Memory Cache MemoryCache memory is a very high speed semiconductor memory which can speed up the CPU. It acts as a buffer between the CPU and the main memory. It is used to hold those parts of data and program which are most frequently used by the CPU. The parts of data and programs are transferred from the disk to cache memory by the operating system, from where the CPU can access them.
AdvantagesThe advantages of cache memory are as follows −Cache memory is faster than main memory. It consumes less access time as compared to main memory. It stores the program that can be executed within a short period of time. It stores data for temporary use. DisadvantagesThe disadvantages of cache memory are as follows −Cache memory has limited capacity. It is very expensive. 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 generally made up of semiconductor device. These memories are not as fast as registers. The data and instruction required to be processed resides in the main memory. It is divided into two subcategories RAM and ROM.
Characteristics of Main MemoryThese are semiconductor memories. It is known as the main memory. Usually volatile memory. Data is lost in case power is switched off. It is the working memory of the computer. Faster than secondary memories. A computer cannot run without the primary memory. Secondary MemoryThis 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. CPU directly does not access these memories, instead they are accessed via input-output routines. The contents of secondary memories are first transferred to the main memory, and then the CPU can access it. For example, disk, CD-ROM, DVD, etc.
Characteristics of Secondary MemoryThese 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. Q10) Explain Secondary storageQ10) You know that processor memory, also known as primary memory, is expensive as well as limited. The faster primary memories are also volatile. If we need to store large amount of data or programs permanently, we need a cheaper and permanent memory. Such memory is called secondary memory. Here we will discuss secondary memory devices that can be used to store large amount of data, audio, video and multimedia files.Characteristics of Secondary MemoryThese are some characteristics of secondary memory, which distinguish it from primary memory −It is non-volatile, i.e. it retains data when power is switched off It is large capacities to the tune of terabytes It is cheaper as compared to primary memory Depending on whether secondary memory device is part of CPU or not, there are two types of secondary memory – fixed and removable.
Let us look at some of the secondary memory devices available.Hard Disk DriveHard disk drive is made up of a series of circular disks called platters arranged one over the other almost ½ inches apart around a spindle. Disks are made of non-magnetic material like aluminum alloy and coated with 10-20 nm of magnetic material.
Standard diameter of these disks is 14 inches and they rotate with speeds varying from 4200 rpm (rotations per minute) for personal computers to 15000 rpm for servers. Data is stored by magnetizing or demagnetizing the magnetic coating. A magnetic reader arm is used to read data from and write data to the disks. A typical modern HDD has capacity in terabytes (TB).CD DriveCD stands for Compact Disk. CDs are circular disks that use optical rays, usually lasers, to read and write data. They are very cheap as you can get 700 MB of storage space for less than a dollar. CDs are inserted in CD drives built into CPU cabinet. They are portable as you can eject the drive, remove the CD and carry it with you. There are three types of CDs −CD-ROM (Compact Disk – Read Only Memory) − The data on these CDs are recorded by the manufacturer. Proprietary Software, audio or video are released on CD-ROMs. CD-R (Compact Disk – Recordable) − Data can be written by the user once on the CD-R. It cannot be deleted or modified later. CD-RW (Compact Disk – Rewritable) − Data can be written and deleted on these optical disks again and again. DVD DriveDVD stands for Digital Video Display. DVD are optical devices that can store 15 times the data held by CDs. They are usually used to store rich multimedia files that need high storage capacity. DVDs also come in three varieties – read only, recordable and rewritable.
Pen DrivePen drive is a portable memory device that uses solid state memory rather than magnetic fields or lasers to record data. It uses a technology similar to RAM, except that it is nonvolatile. It is also called USB drive, key drive or flash memory.
Blue Ray DiskBlue Ray Disk (BD) is an optical storage media used to store high definition (HD) video and other multimedia filed. BD uses shorter wavelength laser as compared to CD/DVD. This enables writing arm to focus more tightly on the disk and hence pack in more data. BDs can store up to 128 GB data.
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Arithmetic and logic unit ::
ALU perform all the arithmetic and logic calculation provided to computer systems that are addition,substraction,multiplication,division,comparison,greater,less.
Control Unit ::
This unit controls and facilitates all the activities and operations performed in the PC system. It gets programs from the main memory of the computer system to interpret or translate them and control other units to get the desired result.
Cache ::
Cache memory dwells between the main memory and processor. The rate of exchanging data and information is substantially higher compared to other memory of computer system. The cache memory saves and holds the data or set of information that is about to process immediately by the system.
The cache memory is not available to users they cannot delete, update, refresh the programs inside the memory, the manufacturer, or the computer programmers can erase or update the data which is stored inside the cache memory.
They are quite expensive therefore they were first introduced or installed in a large computer only in small numbers however as the technology developed the small computer, or desktop computer used cache memory and we usually call them as l1 cache and l2 cache. CPU [Central Processing Unit] | Processor SpeedThe speed of the microprocessor is the essential ingredient as the software technology has developed to the extreme use of large programs and application are made available to users to execute this application high speed of processors are required. The processor speed can be defined and characterized as the speed at which it executes the instructions and directions. The speed of the processor is measured in MHz (Millions of Pulses for each second) and GHz (Billion of pulses for each second)The speed of mini and mainframe computers are measured in MIPS (Millions of instruction per second) and BIPS (Billions of instructions per second). Functions of CPU in ComputerThe CPU Is considered as the brain or heart of the computer as it is responsible for each and every operation performed in a computer system. It controls and organizes every section and unit of a Personal computer. Every instruction passed to a computer system is firstly converted into binary numbers that consist of 0s 1s which is in machine-readable form later this instruction which has been changed over are send to the registry and eventually they are transferred and exchanged to CPU for further and additional processing and preparing as processor have ALU which stands for Arithmetic and logical operation with the help of ALU computer performs every mathematical and logical operation.There are Four Primary Functions of Processor
Decode:: All the program or instruction are translated from assembly language or low level to binary language which helps the computer system to deliver the output in human-readable or intelligent form. This process of conversion and transformation from one language to another is called as DECODING
Execute :: The processor recovers the instructions and data from memory and processes them to get wanted output with the assistance of ALU (Arithmetic and coherent unit).
Store :: After the procedure is finished in ALU. The output is put away in memory for additionally processing. The speed of PC altogether relies on the CPU. The fundamental usefulness of PC can be made fast by introducing present-day processors. Q5) What is VDU?A5) Stands for "Visual Display Unit." A VDU displays images generated by a computer or other electronic device. The term VDU is often used synonymously with "monitor," but it can also refer to another type of display, such as a digital projector. Visual display units may be peripheral devices or may be integrated with the other components. For example, the Apple iMac uses an all-in-one design, in which the screen and computer are built into a single unit.Early VDUs were primarily cathode ray tube (CRT) displays and typically had a diagonal size of 13 inches or less. During the 1990s, 15" and 17" displays became standard, and some manufacturers began producing displays over 20" in size. At the turn of the century, flat panel displays became more common, and by 2006, CRT displays were hard to find.Today, it is common for computers to come with VDUs that are 20" to 30" in size. Thanks to the recent growth in LCD, plasma, and LED technology, manufacturing large screens is much more cost effective than before. Q6) Explain Keyboard and MouseA6) KeyboardKeyboard 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.
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S.No | Keys & Description |
1 | Typing Keys 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 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. |
3 | Function Keys 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. |
4 | Control keys 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). |
5 | Special Purpose Keys Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen. |
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S.No | Keys & Description |
1 | Typing Keys 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 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. |
3 | Function Keys 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. |
4 | Control keys 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). |
5 | Special Purpose Keys Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print Screen. |
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