85595833 notes on 9th computer science by asif rasheed

7/22/2019 85595833 Notes on 9th Computer Science by Asif Rasheed

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NotesComputer

Science 9thClass

July2013

Chapter Introduction to Computers

Chapter: 2 ComputerComponentsChapter: 3 Input / output DevicesChapter:4 STORAGE DIVECESChapteer:5 NUMBER SYSTEMSChapter :6 BOOLEAN ALGEBRA


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Notes on 9th Computer Science

by Asif Rasheed

Chapter: 1 Introduction to Computers

Q.1. What is Computer?Ans. Computer is an electronic device that processes data and converts it intoinformation and gives us results accordingly.

Q.2. What is an ABACUS?Ans. Abacus, a wooden frame of wires and beads, was made by Chinese about 2000

years ago for simple addition.


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Q.3. What is Napiers Bones?Ans. John Napier created a device using rods to perform arithmetic calculations that is

called Napiers Bones.

Q.4. What do you know about Pascaline Calculator?Ans. Pascal invented a machine that had a system of gears. Numbers could be

entered and cumulative sums obtained by cranking a handle.


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Q.5. Who made the Difference Engine?Ans. Charles Babbage designed an automatic mechanical calculating machine that he

called a difference engine.

Q.6. What is Analytical Engine?Ans. Charles Babbage constructed a general purpose, fully program-controlled,

automatic mechanical digital computer that is called analytical engine.

Q.7. What is the use of Punched Cards and who made it?


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Ans. In 1890, Herman Hollerith developed the first electro-mechanical punched cardtabulator that could read information that had been punched into cards.

Q.8. Who made ENIAC?Ans. In 1942, P.Eckert, John W. Mauchly decided to build a high-speed electronic

computer that is known as ENIAC.

Q.9. What is the modern idea of Stored-program and who proposed it?


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Ans. John Von Neumann gave the modern idea of stored-program and according tohim Data and program can be stored in the same memory. Thus the machinecan itself alter either its program or internal data.

Q.10. Write the Technologies and Computers of Computer Generations.Ans.

Generation Technology ComputersG-1 Vacuum Tubes ENIAC & UNIVAC-IG-2 Transistors IBM7094,1400 Series


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G-3 Integrated Circuits UNIVAC 9000,IBM 370G-4 Microprocessor Apple Macintosh, IBM PCG-5 Artificial Intelligence

Q.11. Name the first Digital Computer?Ans. In early 1940s, Aiken built the first general-purpose digital computer called Mark-

I.Q.12. What is a Terminal?


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Ans. A terminal is a monitor and a keyboard connected to a mainframe computer tobuild a network.

Q.13. What is meant by a Virtual Classroom?Ans. In a virtual classroom, the teacher deliver lecture at its own workplace while the

students, connected to a network, may listen to him at their homes. They may putquestions and answers are sent to them via email.

Q.14. Define Universal Production Code.


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Ans. The sequence of lines that is read by a Bar Code Reader. The price of the itemis stored in this code and these are automatically added to the bill.

Q.15. Define Computer Simulation.Ans. Computer Simulation is the use of computer to represent the dynamic responses

of system by the change in behaviors of another system modeled after it.

Q.16. What is a Computer Program?Ans. The set of instructions to solve any kind of problem is called computer program.


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Q.17. Define Low Level Languages.Ans. These languages are quite close to the processor but not even understandable

for human being e.g. machine language, assembly language.

Q.18. Define High Level Languages.Ans. These languages are quite close the human languages like English language

and far from machine language e.g. FORTRAN, BASIC, C/C++, VB.


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Q.19. What is an Assembler?Ans. Assembler is a program that translates an assembly language program into

machine code.

Q.20. What is a Compiler?Ans. Compiler is a program that translates a program written in high-level language

into machine code. It reads the whole program before executing.


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ABBREVIATIONS

ENIAC Electronical Numerical Integrator and Calculator

UNIVAC Universal Automatic Computer

IBM International Business Machine

IC Integrated Circuit

LSIC Large Scale Integrated Circuit

VLSIC Very Large Scale Integrated Circuit

AI Artificial Intelligence

PC Personal Computer

LCD Liquid Crystal Display


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ATMs Automatic Transaction Machines

UPC Universal Production Code

Opcode Operation Code

FORTRAN Formula Translation

BASIC Beginners All-purpose Symbolic Instruction Code

COBOL Common Business Oriented Language

LISP List Processing) Language

VB Visual Basic

PDA Personal Data Assistants


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Chapter: 2 Computer Components

Q.1. What is a Program?Ans. The sequence of instructions given to computer for manipulating data is known

as a program.

Q.2. Define Electronic Data Processing.


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Ans. The process of performing arithmetic and logic operations with the help ofcomputer is known as electronic data processing.

Q.3. What is meant by Computer Hardware?Ans. The physical parts of the computer that you can touch and feel are known as

computer hardware.

Q.4. What is meant by Computer Software?


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Ans. The organized collections of computer data and instructions are called computersoftware.

Q.5. What is Input Unit of computer?Ans. Input unit consists of input devices with which we send data to the central

processing unit e.g. keyboard, mouse, scanner etc.

Q.6. What is Output Unit of computer?


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Ans. Output unit consists of output devices with which we get results e.g. monitor,printer etc.

Q.7. What is System Unit of computer?Ans. System unit consists of motherboard, microprocessor and the peripherals

attached to it.

Q.8. Define System Software.


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Ans. The programs that are responsible for controlling and managing the actualoperations of the computer hardware are called system software e.g. operatingsystem.

Q.9. Define Application Software.Ans. The programs that are used to accomplish tasks specified by the user are called

application software e.g. word processing, spreadsheet etc.

Q.10. Define the working of CPU.


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Ans. CPU is called the brain of the computer and the primary work of CPU is toconvert data from input, process the data and giving results accordingly.

Q.11. Define the working of ALU.Ans. ALU is the combination of Arithmetic and Logic unit and it performs all themathematical and logical operations.


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Q.12. Define the working of CU.Ans. CU consists of circuitry that generates signals to direct the entire computer

system to execute the programs and controls the flow of information through theprocessor.

Q.13. What is meant by BUS?Ans. BUS is the common path that is used to send and receive data and commands to

and from CPU and memory and all I/O devices.


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Q.14. What is Data Bus in Computer System?Ans. It is an electrical path that connects the central processing unit, memory,

input/output devices and secondary storage devices.

Q.15. What is Address Bus in the Computer System?

Ans. It carries address information and connects only central processing unit andmemory.


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Q.16. What is Control Bus in the Computer System?Ans. It carries control information from the control unit to the other units.

Q.17. Define Computer Storage.Ans. Computer Storage is used to store programs and data.

Q.18. Define Main Memory (RAM).


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Ans. It is a type of memory that stores data temporarily and data can be stored andretrieved much faster than the secondary storage.

Q.19. Define Secondary Memory (ROM).Ans. It is a type of memory that stores data permanently and data can be stored and

retrieved but not be re-written.

Q.20. What is meant by PORT?


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Ans. A socket that enables an external device such as printer device to be attached tothe computer.

Q.21. Define Serial Port.Ans. Serial port allows s a serial hardware device to communicate with the computer

by transmitting one bit of information at a time such as mouse, modems andkeyboard.

Q.22. Define Parallel Port.


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Ans. Parallel port lets an external parallel device communication with the computer bytransmitting eight bits of data at a time and eight times faster than a serial port.

Q.23. Define USB Port.Ans. USB is a Plug and Play hardware interface for peripherals such as the keyboard,

mouse, joystick etc.

ABBREVIATIONS


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EDP Electronic Data Processing

CPU Central Processing Unit

ALU Arithmetic and Logic Unit

CU Control Unit

I/O Devices Input and Output Devices

RAM Random Access Memory

ROM Read Only Memory

USB Universal Serial Bus

COM Ports Communication Ports

P& P Plug and Play


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Chapter: 3 Input / output Devices

Q.1. Define Input Devices.Ans. The devices that are used to enter data and instructions into the computer are

called input devices e.g. keyboard, mouse, microphone etc.


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Q.2. What is a QWERTY Keyboard?

Ans. Keyboard is the standard input device used to enter textual data into thecomputer.

Q.3. What are Alphanumeric Keys on Keyboard?Ans. The keys that are used to input alphabet (A-Z) and numbers (0-9) are called

alphanumeric keys.


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Q.4. What are Numeric Keys on Keyboard?Ans. The keys that are used to input numbers are called numeric keys.Q.5. What are Function Keys on Keyboard?

Ans. The keys consist of (F1 to F12) are called function keys and these keys provideshortcuts for doing routine tasks on a computer.

Q.6. What are Cursor Control Keys on Keyboard?Ans. These four keys are used for moving the cursor from its current position to right,


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left, up or down.

Q.7. What is a Mouse?Ans. A mouse is an input device that rolls around on a flat surface and controls the

pointer on a display screen.

Q.8. What is a Trackball?Ans. A trackball is a stationary pointing device that works like a mouse and contains a

ball exposed on its surface. It is mainly used in portable computers.


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Q.9. What is a Joystick?Ans. Joystick is an input device used for games, computer aided designs or

simulations.

Q.10. What is a Scanner?Ans. A scanner is an input device that reads the image present on piece of paper and

transfers the information into a computer where a program can store andinterpret it.


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Q.11. What is a Microphone?Ans. A microphone is an input device used to digitally record audio data such as the

human voice.

Q.12. What do you know about Voice Recognition System?Ans. Voice recognition system use a microphone as an input device and converts a

persons speech into digital data by comparing the electrical patterns producedby the speakers voice with a set of prerecorded patterns stored in the computer.


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Q.13. What is meant by Discrete Speech?Ans. Voice recognition applications require each word to be separated by a distinct

pause to determine where on e word begins and the next stops. This style ofdictation is called discrete speech

Q.14. What is a Light Pen?Ans. Light pen is a light-sensitive input device shaped like a pen. It is used to draw on


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the computer screen or to make menu selection.

Q.15. What is a Digital Camera?Ans. Digital camera is a device that stores images digitally in its memory rather

recording them on film.

Q.16. What is a Disk Drive?Ans. A disk drive is a machine that reads data from and writes onto a disk.


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Q.17. Define Output Devices.Ans. The devices that are used to receive data and information from the computer are

called output devices e.g. monitor, printer, speaker etc.

Q.18. What is a Softcopy?Ans. An electronic version of a document stored on a storage device is called

softcopy.Q.19. What is Hardcopy?Ans. The printed version of an electronic document is called hardcopy.


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Q.20. What is a Monitor?Ans. It is an output device that is used to get result in the form of image and text in

different colors.

Q.21. What is meant by resolution?Ans. The number of pixels on the screen expressed as a matrix is called resolution.

Q.22. What is a CRT Monitor?


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Ans. A phosphors coated screen with three electron guns on its back is called CRTMonitor.

Q.23. What is a LCD Monitor?Ans. LCD Monitor is commonly used in portable computer and it creates images with a

special kind of liquid crystal that normally transparent but becomes opaque whencharged with electricity.

Q.24. Define Video Controller?


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Ans. Video controller is an intermediary device between the CPU and the monitor anddetermines the resolution of the monitor e.g. VGA and SVGA.

Q.25. What is a Printer?Ans. Printer is an output device that produces hardcopy on the paper.

Q.26. What are Impact Printers?Ans. Impact printers produce images by striking an inked ribbon with a hammer or a

set of pins, pressing ink from the ribbon onto a piece of paper.


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Q.27. What are Non-impact Printers?Ans. Non-impact printers produce images on paper without striking the page in any

way.

Q.28. What is a Plotter?Ans. Plotters are used as output device and print a large drawing or image(s).

Q.29. What is meant by CDR?


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Ans. A CDR is a drive that allows for recording information to a CDR disk.

Q.30. What is meant by CDRW?Ans. CDRW is a drive that can use both CDR and CDRW discs. These are the discs

on which old data can be erased and new data can be written.

ABBREVIATIONS

OCR Optical Character Recognition

HDD High Density Disk/Hard Disk Drive


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FDD Floppy Disk Drive

CRT Cathode Ray Tube

LCD Liquid Crystal Display

VGA Video Graphic Array

SVGA Super Video Graphic Array

LPM Line Per Minute

CAE Computer Aided Education


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CAD Computer Aided Design

CAM Computer Aided Manufacturing

CD Compact Disk

CDR Compact Disk Recorder

CDRW Compact Disk Writer and Re-writer.


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CHAPTER 3 INPUT AND OUTPUT DEVICES

(SHORT QUESTIONS)1 What are input devices? Give their two examples.

Ans: The devices that are used to enter data and instructions into the computer are called input devices. Example:keyboard and mouse

2 What is mouse?


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Ans: A mouse is an input device. It rolls around on a flat surface and controls the pointer on a display screen. Atypical mouse has two buttons, which perform different functions depending on what application is running.

3 What is trackball?Ans: A trackball is an input device. It works like a mouse but it is a stationary device with a moveable ball on its top.The ball is rotated with fingers, thumb, or palm of the hand.

4 Define scanners.Ans: A scanner is an input device. It is used to read images and text printed on the paper, converts into electronicform and stores them into the computer.


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5 What is voice recognition?Ans: A system that converts the voice into text or commands is known as voice recognition. In voice recognitionsystem, a microphone as an input device is used.

Voice recognition allows a user to use voice as input. The user speaks through microphone to givecommand to computer such as opening programs, printed documents, shutting down the computer, saving thedocument etc.

6 What is joystick? Also write its uses?


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Ans: Joystick is a live input device. It can move in all directions and is used to control the movement of the pointeron the screen. Usually, joystick is used for games.

7 What is keyboard?Ans: Keyboard is the most commonly used input device. It is used to enter data into the computer. The keyboardlooks like a typewriter keypad, but it contains some extra commands and function keys.

8 What is microphone?Ans: A microphone id an input device used to record audio data as the human voice. It can be plugged into acomputer or any recorder to record voice of human beings.


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9 What is difference between hard copy and soft copy?Ans: The output received on the paper is called hard copy. While the output received on the display screen is calledsoftcopy. Also the output received from computer in the form of sound is known as softcopy.

10 What is mouse event?Ans: Mouse event refers to the activity that can be performing by using the muse. A typical can perform thefollowing events.a) Left Click


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b) Right Clickc) Drag

11 Write names of two devices which are used both as input and output devices?Ans: The devices which are used both as input and output devices are given below:a) Hard Disk Driveb) Floppy Disk Drive12 What are monochrome monitor?Ans: Monochrome monitors can display information in only one colour such as green, amber or white and black asbackground. These three colours are the basic colours and their combinations can display a full range of colours.


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13 What are printers?Ans: Printers are the most commonly used out put devices. T hey are used to print the output on the paper.

14 How many types of impact printers? Write their names?Ans: There are three types of non-impact printers.a) Dot matrix Printersb) Daisy wheel printersc) Line printers


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15 What are output devices? Give its two examples.

Ans: The devices are used to received information (results or output) from the computer are called output devices.Examples: monitors and printers.

16 What are Line printers?Ans: Line printers are similar to the Daisy wheel printers. They print a complete line of characters at once ratherthan a single character at a time. The printing speed of a line printer is from 300 (lines per minute) to 2400 (lines perminute).


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17 What is a Compact Disk Recorder (CD-R)?Ans: A compact Disk Recorder (CD-R) is a drive allows to record information to a CD-R disc. The recordedinformation can be of digital, audio and video, A CD-R disc will hold a maximum of 700 megabyte of data.

18 What is plotter?A plotter is a large scale printer that receives commands from a computer make drawing on the paper with one ormore automatic pens. Unlike a regular printer can draw continuous point-to-point lines.


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CHAPTER 4 STORAGE DIVECES

(SHORT QUESTIONS)Q. 1. What are storage devices?

Ans. The computer storage is also referred to as computer memory. It is used to store the data and program.

Q. 2. What is RAM?


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Ans. RAM stands for Random Access Memory. It is the primary storage device. It stores data and instructiontemporarily.

Q. 3. What is read and write operations?Ans. During read operation the contents of memory location are copied to a central processing unit (CPU) register.Whereas during write operation the contents of a central processing unit (CPU) register are copied to the memorylocation.

Q. 4. What is difference between DRAM and SRAM?


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Ans. DRAM is the most commonly used technology to build RAM chips. It consumes a lot of power as data storedin a DRAM needs to be refreshed periodically. While the contents of SRAM do not need to be refreshed periodicallyand SRAM is faster than the DRAM.

Q. 5. What is a bit?Ans. A bit is defined as the smallest basic unit of storage in the computer memory that has value 0 or1.

Q. 6. What is secondary memory?Ans. The secondary memory or storage is used to store information permanently for future use. A large amount ofdata and programs can be stored into it. Its storage capacity is up to Gigabytes for personal computers.


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Q. 7. What is sequential access storage?Ans. In sequential access storage, the data or records are stored and read in sequential order, i.e. one after theother. The magnetic tape is an example of sequential access storage.

Q. 8. What is data rate?Ans. The data is the number of bytes per seconds that the drive can deliver to the central processing unit (CPU)rates between 5 and 40 megabytes per second are common.

Q. 9. Define seek time?


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Ans. The time used to move the head to the appropriate track after reading the address is called the seek time.

Q. 10. What is relation between a nibble and a byte?Ans. A group of 4-bits sequence is called a nibble. Where as a byte is a group of 8 bits. Thus, one byte is equal to2 nibble.

Q. 11. What is magnetic tape storage?Ans. Magnetic tape is the most popular and oldest secondary used to store large amount of data and instructionspermanently. The magnetic tape is a plastic ribbon and one side coated with magnetic recording material.


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Q. 12. What is floppy disk?

Ans. A floppy disk is mostly used for transferring data between computer systems and for casual backup of data.They have low capacity and are very, very slow as compared to other storage devices. The most common size offloppy disk is 3.5 inches diameter.

Q. 13. What is compact disk?Ans. Compact disk (CD) is commonly used to store data. It can store 700 MB of data. It is very useful for storingaudio and video data.


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Q. 14. How many types of magnetic disk? Write their names.Ans. There are two types of magnetic disk.a) Hard diskb) Floppy diskQ. 15. RAM is a volatile memory. Why?Ans. As the RAM is constructed from integrated circuits so it need to have continuous electrical power supply inorder to maintain. When power is switched off all the data into it is lost. So RAM is a volatile memory.

Q. 16. What is main memory of computer?


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Ans. Main memory is working area of the computer. It is very fast but limited in capacity. A computer cannot workwithout having some kind of main memory. The main memory of a computer consists of thousand or even millionscells each capable of storing a bit i.e. 0 or1.

Q. 17. What is meant by disk format?

Ans. The position of tracks and sectors of a disk are not fixed but these positions are marked by a process calledformat.


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Q. 18. What is backing storage device?Ans. Secondary storage is also called backing storage. It is an addition in main storage. It is very cheap ascompared to magnetic disks. A large volume of data can be stored on the backing device.

CHAPTER 5 NUMBER SYSTEMS

(SHORT QUESTIONS)Q.1. What is the difference between data and information?


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Ans. The collection of raw facts and figures is called data where as the data after processing is calledinformation.

Q.2. What is binary number system?

Ans. The word binary means two. The binary number system uses two digits 0 and 1 to represent any quantity.So, the base of binary number is 2.

Q.3. Convert 011011(2) into decimal.Ans. 011011(2) = 0*25 + 1*24 + 1*23 + 0*22 + 1*21 + 1*20


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= 0 + 1*16 + 1*8 + 0 + 1*2 + 1*1= 16 + 2 + 8 + 2 = 27(10)

Q.4. What is ASCII code?

Ans. ASCII stands for American Standard Code for Information and Interchange. It is the standard code torepresent alphanumeric data.

Q.5. How many types of number system? Write their names.


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Ans. There are four types of number system.a) Decimal number system

b) Binary number systemc) Octal number systemd) Hexadecimal number system

Q.6. What is BCD code? Explain by an example.

Ans. BCD stands for Binary Coded Decimal. It is used to represent numeric data. In this coding scheme, eachdecimal digit is represented by 4-bits.


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BCD equivalent of 247 is given below:Decimal system 2 4 7

0010 0100 0111So, BCD equivalent of 247 = 0001001000111

Q.7. Describe the method to find 1s complement of a binary digit?

Ans. 1s complement of any binary digit can be directly obtained by changing all 0s to 1s and all 1s to 0s.

Q.8. Convert 129 into binary.


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Ans.

2 1292 64 12 32 02 16 02 8 02 4 02 2 0

1 0


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Q.9. What is numeric data?

Ans. Numeric data is used to represent different quantities on which arithmetic is to be performed. Mostly data isrepresented as integers or real numbers e.g. 10, 323, -76.07 etc.

Q.10. What is meant by UNICODE?

Ans. UNICODE stands for universal code. It is a 16-bit coding scheme. It is a popular coding scheme used thesedays.


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Q.11. Convert 1C2(16) into octal.Ans. 1C2(16) = 1+162 + c*161 + 2*160

= 1*256 + 12*16 + 2*1= 256 + 192 + 2 = 450(8)

Q.12. What is alphanumeric data?

Ans. Alphanumeric data contains alphabets, numbers and other special charact ers i.e. $, #, % etc


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Q.13. What is meant by coding?

Ans. The process of representing of numeric or non-numeric data in the form of machine is called coding.

Q.14. Solve 0110(2) * 1011(2)Ans. 0110(2)

1011(2)_______

0110


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0110*0000**

0110***_____________________

1000010(2)So, 010(2) * 1011(2) = 1000010(2)

Q.15. Solve 01001101(2) 111(2)Ans. 01011

111 01001101


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0011110100111

111111000

So, 01001101(2) 111(2) = 01011(2)Q.16. Find 2s complement of 01100110(2)


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Ans. To find 2s complement of the given number, firstly we find 1s complement of given number, so,0100110(2) = 10011001 (1s complement)Now we add 1 in the given result.

10011001+ 1

10011010

So, 2s complement of 01100110(2) is 10011010.


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Q.17. Define a number system.

Ans. A set of values used to represent different quantities is known as number system.

Q.18. Convert 0271.231(8) into decimal.

Ans. 0271.231 = 0*83 + 2*82 + 7*81 + 1*80 + 2*8-1 + 3*8-2 + 1*8-3= 0 + 2*64 + 7*8 + 1*1 + 2/8 + 3*64 + 1/512= 128 + 56 + 1 + 0.25 + 0.046 + 0.00195=185.2988(10)


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CHAPTER 6 BOOLEAN ALGEBRA

(SHORT QUESTIONS)Q.1. What is Boolean Algebra?

Ans. Boolean algebra is the algebra of logic. Boolean algebra uses symbols to represent logical statementsinstead of words.


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Q.2. What are Boolean expressions?

Ans. An expression formed with binary variables, constants, Boolean operators as well as parentheses is knownas Boolean expressions. It is a logical statement which gives result either true or false.

Q.3. What is literal?


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Ans. Suppose two variables x and y are used in a Boolean function. Each variable may appear in the functionin two forms, i.e. it may appear in the complement form or without complement form. Each of these forms is called aliteral.

Q.4. What is identity element?

Ans. There is an identity element 1 with respect to AND (.) such that for A:1 . A = A

There is an identity element 0 with respect to OR (+) such that for A:0 + A = A


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Q.5. What is Karnaugh Map?

Ans. Karnaugh Map is also referred to as K-map. It provides an efficient way to solve / simplify Booleanfunctions. It is a tool used to transform a truth table of expression into a simplified logic circuit.

Q.6. State the theorem: x . (x + y) = x

Ans. L.H.S. = x . (x + y)= x .1 + x . y (Identity element)


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= x . (1 + y) (by distributive law)= x . 1 (1 + y = 1)= x (identity element)

] = R.H.SHence the theorem is proved.

Q.7. What is minterms?

Ans. If two Boolean variables x and y then products using these variables, x . y, x . y,


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x . y, x . y . These are called standard products or minterms with two variables.

Q.8. What is Boolean function?

Ans. A Boolean function is an expression formed with binary variables may an equal sign. The Booleanoperators, parenthesis and equal to either 0 or 1. The value returned by Boolean function is also equal to either 0 or1.Q.9. How many types of logical operators? Write their names.

Ans. There are three logical operators.


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a) OR Operatorb) AND operatorc) NOT Operator

Q.10. State the theorem: x + x = x

Ans. L.H.S. = x + x= x .1 + x.1 (Identity element)=x . (1 + 1) (by distributive law)= x . 1 (1 + 1 = 1)


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= x (Identity element)= R.H.S

Hence the theorem is proved.

Q.11. What are Boolean Constants?

Ans. The quantities that may not change their values are called constants. If B ={0 , 1} then 0 and 1 are theBoolean constants.

Q.12. What is truth table?


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Ans. The table that represents the output of a Boolean expression for all the possible combinations of inputvalues is called the truth table.

TRUTH TABLEOR Operation AND Operation Not OperationA B X= A +BA B X= A . B A X= A

0 0 0 0 0 0 0 10 1 1 0 1 0 1 0


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1 0 1 1 0 01 1 1 1 1 1

Q.13. What is a gate?

Ans. Gate is an electronic circuit that receives one or more than one inputs and gives output. It is used like arapidly working binary switch. It has only two conditions i.e. ON and OFF.

Q.14. What are Boolean Variables?


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Ans. If B = {0,1 with operators dot (.) and (+) is a Boolean algebra, then the variables x, y etc are called Booleanvariables.

Q.15. What are maxterms?

Ans. If two Boolean variables x and y, then sums using these variables, x + y, x + y,

x + y, x + y. These are called a standard sums or maxterms with two variables.


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Q.16. If x = 0, y = 1 and z = 0, then find the value of x . y + x . z + x . y.

Ans. As x = 0, then x = 1

Thus y = 0, and z = 1Now putting the values:= x . y + x . z + x . y= 1 . 1 + 0 . 1 + 0 . 0= 1 + 0 + 0= 1


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Q.17. How many elements of Boolean algebra?

Ans. There are two elements of Boolean algebra.a) Boolean constantsb) Boolean variables

Q.18. What is the function of NOT operator?


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85595833 notes on 9th computer science by asif rasheed

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