SEBA Class IX | computer science | Chapter 1 : Basics of computer system

Excercise :

1. Choose the correct option.

a. Which of the following is not an output device ?

i. Speaker ii. Mouse iii. Printer iv. Monitor

Ans: Mouse

b. Which one of the following is the brain of a computer ?

i. CPU ii. ALU iii. CU iv. MU

Ans: CPU

c. A collection of eight bits is called

i. Byte ii. Word iii. Record iv. Nibble

Ans: Byte

d. Second generation computers were manufactured using which technology ?

i. Vacuum Tubes ii. Transistors iii. ICs iv. None of these

Ans : Transistors

e. Storage of 1 KB means the following number of bytes.

i. 1000 ii. 1024 iii. 1064 iv. 1012

Ans: 1024

f. Which of the following is not hardware ?

i. Hard Disk ii. Printer iii. Assembler iv. CPU

Ans: Assembler

g. Fourth generation computers used

i. Vacuum Tubes ii. Transsitors iii. Microprocessors iv. ICs

Ans: Microprocessors

h. Which one of the following is a special purpose application software ?

i. Word processing software

ii. Operating System Software

iii. Compiler

iv. Payroll system

Ans: Payroll system

i. The base of octal number system is

i. 2 ii. 10 iii. 16 iv. 8

Ans : 8

j. Who is known as the father of the modern computer

i. Charles Babbage

ii. Blaise Pascal

iii. Herman Hollerith

iv. John Atanasoff

Ans: Charles Babbage

2. Fill in the blanks

a. The first – generation computers used ……………………. for storage.

Ans: Magnetic drums

b. The third- generation computers replaced ………………….with ……………………….

Ans: Transistors, Integrated Circuits

c. ……………………… are high speed temporary storage area.

Ans: Registers

d………………………….. is the short form of binary digit.

Ans: BIT

e. A group of four bits is called ……………………

Ans : Nibble

f. ………………………………. holds data, programs and instructions for computer.

Ans: Memory Unit

g. A microphone is a/an …………………..device.

Ans: input

h. A ………………… is a set of instructions to perform a specific task.

Ans: Program

i. ……………………… software are used to scan the computers for viruses.

Ans: Antivirus

j. The decimal system is composed of ………………. digits.

Ans: 10

k. ………………….. was the first fully electronic general purpose computer.

Ans: ENIAC

l. ……………………. was one of the first commercially available computers.

Ans: UNIVAC I

m. A/ An ……………………. converts the program written in assembly language into machine language.

Ans: Assembler

n. Processing takes place in the ……………..

Ans: CPU

o. The ALU performs the …………………. and …………………… operations.

Ans: arithmetic, logical

p. RAM is ………………………….

Ans: volatile/ temporary

q. ROM stores basic ……………………. instructions to operate the computer.

Ans: input/output

r. ………………………..memory is an electronic non-volatile, storage medium that can be electronically erased and reprogrammed.

Ans: EEPROM

s. Data and instructions are given to the computer through its ………………………… device.

Ans: input

t. Raw data is processed by the computer to produce ……………………

Ans: output/ result

u. Results are obtained from the computer through its ………………………. device.

Ans: output

v. 1 MB= ……………….. KB

Ans: 1024

w. …………………….. is an example of primary memory.

Ans: RAM

x. The octal number system uses the digits from……………… to ……………….

Ans: 0, 7

y. A computer system comprise of both …………………. and …………………..

Ans: hardware, software

z. ………………………. represents the set of programs that directs the computer how to work.

Ans: Software.

3. State true or false

a. Another name for internal memory is primary memory

Ans: True

b. A hard disk can store less data than CD

Ans: False

c. Software represent to the physical components of a computer

Ans: False

d. A projector is input device

Ans: False

e. Interpreter is an utility software.

Ans: False

f. The first-generation computers used transistors.

Ans: False

g. Atanasoff Berry Computer was the first electronic digital computer.

Ans: False

h. IBM 604 is an example of second-generation computers.

Ans: True

i. UNIVAC I was one of the first commercially available computers

Ans: True

j. ROM is volatile

Ans: False

k. A group of eight bits is called nibble

Ans: False

l. Computer does not understand any language other than machine language

Ans: True

m. Pen drives use flash memory to store data

Ans: True

n. The monitor is a soft copy output device.

Ans: True

o. A compiler translates a program written in machine language into a program written high level language.

Ans: False

p. Bit is the smallest unit of data in a computer.

Ans: True

4. Short answer questions

a. Who is known as the ‘father of the modern computer’?

Ans: Charles Babbage

b. What is a computer ?

Ans: A computer is an electronic machine which accepts data and instructions from a user, processes the data as per the instruction given by the user and gives the result to the user.

c. Name a popular pointing device.

Ans: Mouse

d. Who invented Jacquard’s loom

Ans: Joseph Jacquard

e. Give the full form of ENIAC and EDVAC.

Ans: ENIAC stands for Electronic Numerical Integrator And Calculator.

EDVAC stands for Electronic Discrete Variable Automatic Calculator.

f. Give two examples of second generation computers .

Ans: IBM 604, IBM 1401

g. What is AI ?

Ans: AI is an emerging branch in computer science which interprets the means and methods of making computers think like human beings. With AI, a machine particularly a computer can become intelligent like human being.

h. Give two examples of secondary memories.

Ans: Hard Disk, Compact Disk

i. What does the CPU do ?

Ans: CPU is the processing unit of a computer. It performs all types of processing on data. CPU is also responsible for controlling the operations of other units of a computer system.

j. Why we use secondary memory ?

Ans: As the primary memory of a computer is volatile and has less storage capacity we use secondary memory so that we can store a large amount data and instructions permanently for later use.

k. Give two example of pointing devices ?

Ans: Mouse and Track ball.

l. Which input device is used to record sound ?

Ans: Microphone

m. What is the use of Barcode Reader ?

Ans: Barcode Reader is used to read information stored in bar codes. Barcodes are the long vertical or horizontal stripes.

n. What is a system software ? Give two examples.

Ans: System software is a set programs used to control hardware and operate a computer. It helps in the smooth functioning of a computer system.

It provides a platform for running various application software in a computer. System software is classified in three categories such as Operating System, Language Processors and Utility software.

Two examples of system software are Windows operating system, Quick heal antivirus.

o. What is the role of CU ?

Ans: CU controls and coordinates between the operations of other units of a computer system. It does not process the data but controls the entire processing of data inside the processing unit.

p. What is the function of ALU ?

And: ALU performs arithmetic calculations such as addition, subtraction, Multiplication, division etc. It also takes logical decisions such as <, > <=, >=, == example. comparisons among data.

q. What do you understand by memory word ?

Ans: By memory we mean the storage space available in a computer for storing data and instructions for immediate use.

r. What is the function of compiler ?

Ans: Compiler is a translator which converts/translates high level language into machine language.

s. What is the main limitation of a computer ?

Ans: The main limitation of a computer is that it can not take any decision on its own. It works according to the instruction given by user.

t. Mention any three main features of a computer.

Ans: Speed, Accuracy, diligence.

u. What is a computer program ?

Ans : A computer program is a set of instructions used to perform various tasks.

v. What are the fundamental components of a computer system ?

Ans: The fundamental components of a computer system are Input unit, Processing unit and Output unit.

w. What is application software ?

Ans: Application software is a group of programs used to perform some specific tasks.

x. Mention various categories of application software ?

Ans: General – purpose application software

Specific -purpose application software

y. What do you understand by computer memory ?

Ans: By Computer memory we mean the storage locations to hold data and instructions for later use.

z. What is the binary equivalent of hexadecimal 15 ?

Ans: 1111

5. a. Mention four features of a computer system ?

Ans: Following are the features of a computer system,

1. Speed: A computer works at a very high speed. It gives us the result in a second no matter how complex the calculation is.

2.Accuracy : A computer always gives us accurate results. It never makes any mistakes. If the question is correct, the answer produced by the computer will also be correct.

3.Diligence: A computer never gets tired. It does not get bored of doing the same work over and over again even if it has  to do the same work million times, it does giving 100 Percent correct result.

4.Versatility: A computer is very versatile. It can perform a series of different tasks one after another.

b. Mention the characteristic features of third-generation computers ?

Ans: The characteristic features of third generation computers are ,

i. The third generation computers are characterised by a new hardware technology that is Integrated Circuit. It was a thin chip made of silicon in which many transistors were packed.

ii. Because of the use of Integrated Circuit , the computers became more smaller, more reliable and more faster.

iii. The computers in this generation used to consume less electricity.

iv. Semi conductor memories were used as main memory replacing earlier technology.

v. Certain new techniques such as pipelining and multiprocessing were introduced to increase the speed of program execution.

c. What do you understand by generation of computers ? Mention two disadvantages of first generation computers ?

Ans: Generation of computer refers to the advancements of new computer technology. Generation of computer is often used in relation to the hardware of computers.

Generations of computers were made based on the technological advancement, size, power of the computer etc.

Two disadvantages of first generation computers are

i. The size of the computers were very large in size that is why It occupied a lot of space.

ii. It produced a lot of heat resulting in frequent breakdown.

d. Describe the functioning of CPU .

Ans: CPU is called the brain of a computer. It is the processing unit of a computer. All calculations on data whether it is arithmetic or logical are performed inside CPU.

CPU consists of three parts

i. ALU

ii. CU and

iii. Memory Unit

ALU performs arithmetic calculations on data. It also performs comparisons among data such as whether numbers are equal, greater than, less than etc.

CU is responsible for controlling and coordinating the operations of other units in a computer system.

It works like a manager of a company. It does not process data but it controls the processing of data inside CPU.

Memory Unit stores data and instructions feed by input device in a computer. It stores data and instructions immediately needed by CPU for processing. It holds data before and after processing is done.

f. What are the categories of printers ? Explain .

Ans: Printers are divided into two distinct categories such as

a. Impact printers and

b. Non impact printers

a. Impact printers: Impact printers are those printers in which there exists physical contact between the print head and the surface it prints on. It operates by striking a metal or plastic head against an ink ribbon. The ink ribbon is pressed against the paper marking the page with appropriate character, dot, line or symbol.

Impact printers are subdivided into two categories such as Line printers and character printers.

Line printers as the name suggests prints one line at a time. Example of line printers are Drum printer and chain printer.

Character printer prints one character at a time.

Example of Character printers are Letter quality printer and Dot Matrix printer.

b. Non-impact printers : Non-impact printers are those printers in which there is no physical contact between the print head and the surface it prints on. Non impact printers are faster than impact printers.

Non-impact printers are divided into four categories such as Inkjet printers, Thermal printers, electromagnetic printer and Laser printer.

g. What is a bus ? Explain three types of buses .

Ans: A bus in a computer system is an electric wire which connects various components attached to it and transfer data between them.

There are three types of buses such as

i. Data bus

ii. Address bus

and iii. Control bus.

Data bus: It carries data from memory to the CPU and CPU to the memory. It is bidirectional.

Address bus: It carries address or location of the data from CPU to the memory.

Control bus: It carries instructions or control signals between CPU and other components of a computer system.

h. What are the functions of primary storage area ?

Ans: The functions of primary storage area are as follows-

i. It holds data and instructions entered through input device until it is sent to the processing unit.

ii. It holds intermediate results while data is being processed .

iii. It holds final results after data is processed until it is sent to secondary storage area.

i. Explain three types of ROM.

Ans: The three types of ROM are

a. PROM: PROM stands for Programmable Read Only Memory. It is a type of ROM where a user can store information once which is not erasable.

b. EPROM: EPROM stands for Erasable Programmable Read Only Memory. It is type of ROM where the contents stored in it can be erased by exposing it to ultra violet light.

c. EEPROM: EEPROM stands for Electrically Erasable Programmable Read Only Memory. The information stored in it can be rewritten by erasing it electrically.

j. What is the purpose of language processor ? Explain the three language processor.

Ans: Language processor is a system software which translates program written in high level language and assembly language into its equivalent machine language.

The three types of language processor are Assembler, Compiler and Interpreter.

Assembler: Assembler translates program written in assembly language into its equivalent high level language code.

Compiler: Compiler translates program written in high level language into its equivalent machine language in one go.

Interpreter: Interpreter translates the program line by line written in high level language into its equivalent machine language.

k. Differentiate between data and information.

Ans: Data means raw facts. Whatever we enter on the keyboard is called Data. Data may or may not have any meaning Whereas Information is the arrangement of data in an organized manner. In other words Information is the processed data.

l. Write short note on fifth generation computers.

Ans:

• Fifth generation computers are based on a new hardware technology i.e. ULSI (Ultra Large Scale Integration). In ULSI millions of components can be stored in a single chip.
• Fifth generation computers are based on parallel processing in which several instructions can be executed parallely resulting in faster execution.
• The new software technology used in fifth generation computers is Artificial Intelligence which includes areas like Expert system, Speech recognition and Voice recognition etc.
• In fifth generation computers RAM, ROM are used as primary storage.
• HDD & SDD are used as secondary storage.
• Various high level languages were developed in this generation of computers like C, C++, Java, Python .Net etc.

m. What are the basic differences between the fourth generation of computers ?

Ans: The basic differences between four generations of computers are as follows-

First generation computers

• The size of the computers were very large in first generation computer. It occupied a lot of space.
• Vacuum Tubes were used in computers.
• It produced a lot of heat resulting in frequent breakdown.
• The programs or instructions given to the computers were in machine language.
• Punched cards were used as input devices.
• Magnetic tapes and magnetic drums were used as secondary memory.
• Computer was accessible to only one programmer at a time
• Examples of first generation computers are ABC, ENIAC, Von Neuuman machine, EDVAC, UNIVAC

Second generation computers

• Second generation computers were technologically more advanced than the first generation computers.
• Transistor was used instead of Vacuum Tubes in computers.
• The computers were were smaller in size as compared to first generation computers.
• Use of transistors increased the operating speed and storage of computers.
• The operating cost of the computers reduced.
• Because of use of transistors less heat were generated resulting in fewer breakdowns in computers.
• The computers were reliable and faster than first generation computers.
• A language was developed for writing programs which consists of alphabets and numbers called as Assembly language but it was still difficult to write and understand. This brought about the development of high level language. This language was made from English words. The program were easier to write and understand.
• The various computers developed during this period were IBM 1400,IBM 7040, CDC 3600, GE 635, B300 etc.

Third generation computers

• The third generation computers are characterized by a new hardware technology that is Integrated Circuit. It was a thin chip made of silicon in which many transistors were packed.
• Because of the use of Integrated Circuit , the computers became more smaller, more reliable and more faster.
• It resulted in reduction in cost of the computers
• The computers in this generation used to consume less electricity.
• Semi conductor memories were used as main memory replacing earlier technology.
• Certain new techniques were introduced to increase the speed of program execution. These techniques were pipelining and multiprocessing.
• The various computers developed in this generation are IBM 360, Honeywell 200, B2000, ICL 1900 etc.

Fourth generation computers

• Fourth generation computers are characterized by LSI i.e. Large Scale Integration and VLSI i.e. Very large Scale Integration. In this technology thousands of transistors could be packed in a single chip making the computers more faster.
• The computers became more lighter and thinner.
• The cost of the computers reduced.
• The computers used to consume less electricity.
• The computers used to produce less heat so there was no cooling requirement.
• The microprocessor were developed in this generation of computers
• Sharing of resources were done using various networks
• Many operating systems were developed like MS DOS, UNIX, Windows, Macintosh etc. during this period.

n. Write a short note on Mark I.

Ans: Howard Aiken an American Computer Engineer with the support of IBM built the first electromechanical computer named Mark I in 1943.

It was able to multiply two 10 digit numbers in 5 seconds. It was the first machine which could perform to pre programmed instruction automatically.

It was the first operational general purpose computer.

o. Explain the two main types of secondary memory.

Ans: The two main types of secondary memory are magnetic Media and Optical Media.

Magnetic Media

The two types of Magnetic media are (i) Magnetic Disk and (ii) Magnetic tape .

Magnetic Disk : Magnetic Disk is coated with magnetic material. It is composed of many tracks and sectors. Each track has its own read/ Write head for reading and writing data on disk.

The examples of Magnetic Disks are Floppy Disk and Hard Disk.

Magnetic Tape :

Magnetic tape is similar to casette tape we used to record and play music. The reel was made of polyster. It can be reused after modifying or erasing old data in it. Magnetic tape drive is required for reading and writing data in it.

Optical Media:

The optical Media are the optical disks and Solid State storage devices where information are stored and read using laser beam.

Optical Disk:

It is a flat circular disk and also a lightweight, portable storage device.

Examples of Optical Disks are CD, DVD, Blu Ray Disk.

Solid State Device:

These devices use flash memory. Examples of Solid State storage devices are Pen Drive, Memory Card etc.

p. Describe various types of magnetic media.

Ans: The various types of magnetic media are (i) Magnetic Disk and (ii) Magnetic Tape

Magnetic Disk:

Magnetic Disk is a circular disk which is coated with magnetic material to store data. The disk is composed of many tracks and sectors. Each track has its own read/ Write head for reading and writing data on disk. The example of Magnetic Disks are Floppy Disk and Hard Disk.

Floppy Disk

It is a circular disk enclosed in plastic box. It was a portable, lightweight removable storage device. There were three sizes of floppy disk such as 3.5 inches, 5.25 inches and 8 inches. It could store data up to 1.44 MB. As computers data and programs are becoming large in size, floppy disk having lesser storage capacity can not accomodate those. That is why it has been replaced by other storage devices now a days.

Hard Disk

Hard Disk is a high capacity storage device which consists of several rapidly rotating disks called platters. Each platter is coated with magnetic material to represent data. Each platter has two read/ write heads, One for each side of the disk. The whole equipment is packed in a sealed container to prevent the surface of platters from heat, smoke, dirt etc.

Magnetic Tape:

Magnetic tape is similar to cassette tape we used to record and play music. It can be reused after modifying or erasing old data in it. Magnetic tape drive is required for reading and writing data in it.

q. Mention some areas where computers are used widely.

Ans: Following are the areas where computers are used widely

(a) Education: Today computer has become an important part of one’s education. computers are used in educational field by teachers for taking online classes, online examination, maintain students records etc. Students use computers to access internet, do projects and research works.

(b) Banks: Almost every bank uses computers to keep the records of money transactions and financial documents. computers are also used to store the details of customers and conduct transactions.

(c) Medical field: computers have become an important part in hospitals, labs and pharmacies. computers are used to keep records of patients and medicines. computers are used in diagnostic system and patient monitoring system.

(d) Communication: Communication has become very easy and simple through internet and email. Internet helps us to find information on any topic. It is the easiest and fastest way of communication. we use computer to communicate with each other through email, chatting, video conferencing.

(e) Business: Computer has now become an integral part of corporate life. Now a days computers can be found in every store, supermarkets, restaurants, offices etc. We can buy and sell things online, pay premium, pay bills etc.

r. What are the major operations performed by a computer ?

Ans: A computer performs the following major operations

(i) Input: The first major operation performed by a computer is to accept data and instruction from a user.

(ii) Process: After accepting data and instruction from a user, computer starts processing on data according to the instruction given by the user.

(iii) Output: The third major operation performed by a computer is to provide the result to the user.

(iv) Store: Another major function performed by a computer is to store the result in secondary storage devices.

s. Differentiate between the following pairs.

I. Input unit and Output unit

Ans: The differences between Input unit and Output unit are as follows,-

Input unit	Output unit
Input unit consists of input devices that can be attached to a computer.	Output unit consists of output devices that can be attached to a computer.
It is used to enter data and instruction into a computer.	It is used to provide result to the user
The example of input devices are keyboard, Mouse, Scanner, Microphone, Light pen etc.	The example of output devices are Monitor, Printer, Plotter, Speaker etc.

II. RAM and ROM.

Ans: The differences between RAM and ROM are as follows-

RAM	ROM
RAM stands for Random Access Memory.	ROM stands for Read Only Memory.
The data and instruction stored in RAM gets erased when the computer is switched off or power supply is stopped.	The data and instruction stored in ROM does not get erased even if the computer is switched off or the power supply is stopped.
RAM is called temporary or volatile memory.	ROM is called permanent or non volatile memory.
we can read as well write data in RAM	data stored in ROM can not be written. It can only be read.

III. Soft copy and hard copy

Ans: The differences between Soft copy and hard copy are as follows-

Sl. No.	Soft copy	Hard copy
1	The information that is displayed or shown in computer screen is called soft copy.	whereas the same information when printed on paper is called hard copy.
2	A Soft copy is a digital copy of a document which resides in an electronic device.	whereas hard copy is a physical copy which exists in real that we can touch and feel.
3	A Soft copy is temporary as it can be edited, modified without getting noticed by user.	but hard copy is permanent as it cannot be edited, modified without getting noticed by user. It will be clearly visible to the user unlike soft copy.
4	A Soft copy is much more convenient in the case of portability. It is easily portable.	but a hard copy is not so convenient to carry to other places because of its weight.
5	A soft copy can be in the form of text, image, audio and video.	whereas hard copy can only be in the form of text and image.
6	A soft does not occupy physical space as it resides in electronic device. It occupies only memory space in electronic device.	whereas hard copy occupies physical space as it exists physically with us.
7	A Soft copy does not have a physical weight.	whereas a hard copy has a physical weight as it exists physically in real.
8	A soft copy can only be created with the help of an electronic medium in electronic devices.	but to create a hard copy we don’t need any electronic medium. It can be created manually with pen, pencil, paper etc.
9	If any hardware failure occurs, we may lose the soft copy. So it is dependent on hardware’s working condition.	but it is not the case with a hard copy. It is not dependent on any hardware. we don’t lose a hard copy if we keep it carefully in a safe place.
10	A soft copy is not so reliable as it is dependent on electricity, hardware’s working condition etc.	But a hard copy is much more reliable than a soft copy as it exists physically.

IV. Primary memory and Secondary memory

Ans: The differences between Primary memory and Secondary memory are as follows-

Primary memory	Secondary memory
Primary memory is also called main memory or internal memory.	Secondary memory is also called External or auxiliary memory.
The data and instruction stored in primary memory lasts for short period of time.	The information are stored in Secondary memory on a permanent basis.
Primary memory has limited storage capacity	Secondary memory has more storage capacity.
Primary memory is expensive	Secondary memory is less expensive than Primary memory
Primary memory communicate directly with CPU.	Secondary memory does not communicate directly with CPU.

V. Impact printer and non-impact printer

Ans: The differences between impact printer and non- impact printer are given below

impact printer	non impact printer
In impact printer there is a physical contact between the print head and paper.	In non-impact printer there is no physical contact between the print head and paper.
Impact printers are slower than non-impact printers	Non-impact printers are faster than impact printers.
The example of impact printers are Dot matrix printer, Line printer, Character printer	The example of non-impact printers are Ink jet printer, Laser printer, thermal printer etc.

VI. Assembler and Compiler

Ans: The differences between Assembler and Compiler are as follows-

Assembler	Compiler
Assembler converts program written in assembly language into high level language.	Compiler converts high level language program into machine language.
GNU is an example of Assembler.	Turbo C ++ is an example of compiler.

VII. Hardware and Software

Ans: Hardware and Software are different from each other in the following ways-

Hardware	Software
The physical components of a computer are called hardware.	Software is the group of programs used to carry out some specific tasks.
Hardware can been touched and felt.	Software can not be touched and felt.
Hardware can not do any task on its own.	Software instructs the hardware to do tasks.

VIII. System software and Application software

Ans: The differences between System software and Application software are as follows-

System Software	Application software
System software manages and controls the working of entire computer system.	Application software used to perform a specific task in a particular field.
The examples of System software are Windows operating system such as Windows 7, 8, 10 etc. Utility software such as various antivirus software, Language processor such as compiler, interpreter, Assembler etc.	The examples of Application software are MS Office suite, Internet Explorer, Adobe Acrobat Reader, Oracle etc.