Chapter 1 : Computer system

Introduction

Computer is an electronic device device derived from the Latin word “computere” which means to calculate. It accepts raw facts and figures as an input which are isolated and uninterpreted through input device, process it according to the requirement of the user or command supplied by the user, store it before and after processing of require and produce a meaningful information as an output through an output device. Generally, computer works on IPO (Input-Process-Output) cycle. It follows GIGO (Garbage In Garbage Out) algorithm which means the output is always based on the input supplied by the user. The basic operation of computer is illustrated by following block diagram.

Some characteristics/features of computer.

The implementation of computers are not only limited/confined to a small area rather they are used from simple domestic task to complex scientific research to engineering. The use of computer are increasing day-by-day due to some special features or characteristics that computer own. Several features of computer are:

1. Accuracy: Computer are the accurate machine that means result produced by computer are 100% accurate. Since, it follows GIGO. The error that may arise in output is due to human not by a computer.
2. Speed: Computer works on tremendously high speed. The operating speed of computer are measured in  millisecond, microsecond, picosecond and nanosecond which means computer can perform millions and billions of instruction per second.
3. Storage: It is the area or unit which is capable of storing data and information for present and future use. Storing data allows users to retrieve it whenever required. These days computer comes with high volume of memory which are measured in Megabyte (1024 KB) , Gigabyte (1024 MB), Terabyte(1024 GB) and Petabyte(1024 TB).
4. Versatility: Computer are generally design to serve more than one type of work. The implementation of computer are not only limited to specific purpose, they solve general requirement of the user and can be used in more than 1 type of job.
5. Diligence: The feature of computer in which computer doesn’t get tired even after working for long period of time. Computer can perform any number of task continuously until it is accomplished. Once the instruction is given computer follows the command till it gets terminated.
6. Automatic: Computer is an automatic machine. Once the instruction is generated it perform accordingly until command is terminated. We don’t have to issue continuous command in order to operate the computer. This is called automatic.

Applications/Implementations/Uses of computer

    The uses of computer are increased day by day. Every aspect if human life is highly influenced by computer. From simple domestic use to complex engineering and scientific solutions, computer can be used. This is due to the versatility of computer. Some of the basic implementation of computer are:

1. Education: Nowadays, computer are highly used in teaching and learning process. Many interesting graphics can be made and provided for easy learning. Also, computer provide features of internet which make learning easy and fun.
2. Communication: Computer is massively used in communication. Communication is done by e-mail, chat, online conferencing. e-fax etc with help of internet in computer. It has made the communication faster, easier and cheaper.
3. Business: In business sector, computer are used to generate invoice, maintain stock and make statistical analysis. E-commerce is the new and emerging way of buying and selling goods and service through used of electronic means and media.
4. Engineering and designing: Scientific and engineering design requires complex and massive computations. Design of bridges, towers, buildings, generators, motors, electrical transmission etc requires precise computation which are done through computers.
5. Science and research
6. Military
7. Industry
8. Medicine
9. Robotics
10. Transportation

Capabilities and Limitations of computer (Pros and Cons)

Capabilities/Advantages/Merits/Pros of computer:

1. Computer is capable of handling larger volume of data and can store huge amount of data.
2. Computer can perform millions of instruction within a limited time frame with same speed and accuracy.
3. Computer are used to fulfill the general requirement of user.
4. It provides faster and cheaper way for communication.
5. Computer are used to solve complex and critical situation in which involvement of humans are almost impossible.

Limitations/Disadvantages/De-merits/Drawback/Cons of computer:

1. Computer is a dull machine, it cannot make their decision on their own.
2. Computer requires electricity or battery in order to operate.
3. It can affect human eye, when used for long period of time.
4. It requires several peripheral devices and software to run.
5. It cannot think, learn or react as human.
6. It cannot draw conclusion and provide feedback.

Generations of computer.

History of computers dates back to mechanical era where computer were not used for general purpose. It takes long period of time to come to this phase. Development of computer had passed through different era from mechanical to electro mechanical to digital computer. The development in different electronic components, precise engineering and hi-tech technology has change the operation of computer drastically. Earlier computer were only used for specific purpose such as counting and performing basic mathematical operation. Later on, due to the necessity and requirement of user different general purpose computer were developed. Therefore, the classification of computer on the basis of major electronic component, their architecture and modes of operation is known as generations of computer. Five different generations of computer are listed below along with their distinct features.

1. First generations computer (1946-1958 )

• They used vacuum tubes as their basic electronic components used to control and amplify electronic signals.
• They were big in size, consume more electricity and generate large amount of heat thus required air conditioning system to keep device cool.
• They were unreliable and were prone to frequent hardware failure.
• They were normally not used for commercial purpose.
• Machine level language was used to program these computers.

eg: ENIAC, EDVAC, EDSAC, UNIVAC

2. Second generations computer (1959-1964 )

• They used transistors as their basic electronic components.
• They were small in size as compared to first generation thus consume less electricity and generate less heat.
• They were less prone to hardware failure thus more reliable.
• They were not also for commercial purpose because production was difficult and costly.
• Assembly language were used to program these computers.

eg: IBM 7000, IBM 1401, IBM 1620, NCR 304, MARK III, ATLAS

[Note: First computer brought in Nepal was IBM 1401 for population census of 2028 BS]
 

3.Third generations computer ( 1965-1974 )

• They used Integrated Circuits (IC) as their basic electronic components.
• They were smaller in size, consume less electricity and generate less amount of heat.
• They were faster and more reliable compared to first and second generations.
• They were widely used for the commercial application all over the world.
• High level language were used to program these computers.

eg: PDP-8, PDP-11, ICL 2900 series, IBM 360, IBM 370

4. Fourth generation computer (1975-1990)

• They use VLSI ( Very Large Scale Integrated Circuits ) as their main electronic components.
• There size were drastically reduced and hence were they were much more portable.
• They were faster in processing and were much more reliable.
• They have larger memory up to GB and TB.
• They use different advance high level language to program this computer.

eg: Apple Macintosh,  IBM PC

5. Fifth generation computer (1990-onwards)

• They use ULSIC (Ultra Large Scale Integrated Circuit) or Microprocessor as their major electronic components.
• They have or will have artificial intelligence.
• They have tremendously high processing unit due to parallel processing.
• They are capable of image processing, speech or voice recognition.
• They use different high level language to program this computer.

Introduction to computer system

The word system refers to the integration of several individual independent unit which are integrated together to achieve a common objective or goal. System is a set of detailed method, procedure and routines created to carryout a specific activity, performs a duty or solve a problem. In a system different unit co-ordinate with each other so that they work as a whole. Without any of the unit whole system is affected.
Similarly. computer system is also a Combination on hardware, software and peripherals which are organized together to run our computer system smoothly. Basically, our computer System works on IPO (Input Process Output) cycle. So, it is mandatory/compulsory to have different unit work together as a whole in order  to convert raw facts and figure into meaningful information. Without any one of these unit computer starts malfunctioning. 
The design, arrangement, construction or organization a different parts of computer system is known as computer architecture. It is the conceptual design and fundamental operational structure of a computer system. It is a framework which focus in how CPU performs internal operation. So computer architecture may also be define as the science and art of selection, inter connecting hardware components to create computer to meet functional performance and cost.

Components/Elements of Computer System

A Computer System has several have several basic components or elements which are listed below:
 1. Hardware ( Input, Output, Processing and storage )
 2. Software
 3. Data/Information
 4. Procedure
 5. People
 6. Communication


Hardware: Hardware is the physical devices on the computer which we can touch and see With out hardware, software cannot work it include input device, output device, processing device and storage device for example: device like keyboard, mouse, CPU, hard disk and RAM are commonly  used hardware devices.
Software: The collection set of instruction is known as program.which performs some specific function. These programs are integrated together in order to work as a software. Software describes how hardware should function and helps in popper utilization and mobilization of computer hardware.For eg. Operating system, MS-Office, Billing software etc.
Data/Information: The raw facts and figures that are isolated, uninterpreted, and doesn’t give any sense is known as data. Data are fed into the computer for processing as a input though Input devices. Whereas, the meaningful result obtained after processing data according to the supplied instruction is known as information. Information generally are the processed version of data which are obtain as output through output device.
People/User: It is the most important part of the computer system. People operate the computer hardware and create the computer software.  People helps to generate command to operate the computer system. Without user no hardware and software can be mobilized.
Procedure: Procedure are the description of how things are done.It includes steps for converting raw fact and figure into meaningful information. It include the general guidelines of how computer should be used.
Communication: Once the computer system is setup,  there is tremendous amount of data flow between user to computer and vice-versa. The data are shared among different components of our computer System in the form of electronic signal. The exchange of data and information between several components can also be termed as communication.

Basic hardware components of a computer system.

1. Input unit
2. Output unit 
3. Processing unit
4. Storage unit

Input Unit: Data and instruction must enter the computer system before any computation can be perform on the supply data. Input device accepts data and instruction from the user, hence the device or the unit which is used to fed raw facts and figures to the computer system  for processing along with set of instruction is called input unit. 
It also converts input data into suitable form that is accepted by the computer System. Generally, it act as a interface/bridge or medium through which communication between user and computer takes place. In short following are the functions performed by the input unit
    1. It accepts the list of instruction and data from the outside world.
    2. It converts the supplied instruction and data into computer acceptable form that is binary code.
    3. It supplies the converted instruction and data to the computer system for further processing.
Some of the commonly used input device are:
Keyboard , track pad, touchscreen, mouse, light pen, scanner, BCR, MICR, OCR, joystick ,trackball etc

Output Unit: The job of an output unit is just the reverse of an input unit. It supplies information and result of computation to the outside world. Thus, it links computer with the external environment. It consists of device that translate information processed by the computer into a form that human can understand. The computer processed information consist of Os and 1 which need to be translated into letters, numbers, special symbols, pictures etc that people can understand. In short following are the function performed by an output unit:
    1. It accepts the result produce by the computer which is not understandable to us.
    2. It converts the result into human understandable form.
    3. It supplies the converted results to the outside world.
Commonly used output device are:
Monitor, printers, speakers, plotters etc.
    There are two types of output device.
                i.  Hard Copy output 
                ii. Soft Copy output

Hard copy output: These type of output are in print form on the paper or some material that can be touched and carried for being shown to other. It is permanent in nature. So that we can look after these output even there is no computer. Unlike soft copy output, these type of output does not need continuous supply of power. for example, Output produce in paper or other material by printer or plotter is known as hard copy output and the device is known as hard copy output device. The commonly used hard copy output devices are printer and plotter.
Soft copy output: Soft copy output refers to the data shown on display screen or produced by speaker. These type output is untouchable. It is temporary in nature that means, output cannot be carried for being shown to others. These types of output resides only when there is computer or continuous electric supply. It is non-portable compared to hard copy output. for example, Output produced on display screen or sound produced from speaker are soft copy output and whereas the device is known as soft copy output device. The commonly used soft copy output devices are speaker and monitor.

Q. Differences between impact and non-impact printers?

(Important question of NEB 11 board exam)

Central Processing Unit: The CPU is brain of any computer system. Like in human body, all major decision are taken by the brain Similarly, in computer all major calculation and comparison are made inside the CPU and CPU is also responsible for activating and controlling the operation of other unit of a computer system A micro processor is a single chip that performs the function of CPU in micro-computers. The speed of the microprocessor is measured in terms of Megahertz and Gigahertz. The functions of CPU (processor) are:
out processing command and co-ordinate with all other parts of computer System:
    i. To carry out processing.
   ii. To give command and co-ordinate with all other parts of computer system.
  iii. To control the sequence of operation that takes place in our computer system. 
  iv. To helps in memory allocation and controls storage of data and instruction.
The central processing unit consists of unit.
 1. Arithmetic logic Unit (ALU) 
 2. Control Unit (CU)
 3. Memory Unit (MU)

ALU: ALU stands for Arithmetic Logic Unit. It is one of the most important  unit of processing. Where actual execution of the instruction takes place during processing. It performs arithmetic and logical operations and controls speed of those operations as directed by control unit(CU). To be clear all the calculation and decision are made in ALU. The data and instruction are stored in the primary memory before processing, and are transferred when needed to the ALU. ALU is designed to perform fundamental mathematical operations such addition, subtraction, multiplication, division and logical Operation which perform Comparison between the two or more than two operands to make a solid decision also known as logical operation which consists of logical OR, logical AND and logical NOT.

CU: Although, control unit doesn’t perform any actual processing on the data , it acts as a central nervous system for other component of the computer. It manages and co-ordinate the entire computer system. It obtain instruction from the program stored in the main memory, interprets the instruction accordingly and issue signal that cause other unit of the system to execute them. Basically, it controls overall operation of the computer. It also controls all other device input/output device connected to the CPU. It directs the movement of electrical signal between main memory to ALU and input-output device. Hence, control unit acts as the nerve system of the computer system.

MU: Memory unit is responsible for storing data and instruction either for short or longer period of time. Basically memory unit stores data and instruction before and after processing . As we know, memory are needed for program being currently used or to store data and instruction permanently . Depending upon the nature of data stored memory unit are distinguished into primary memory and secondary memory. Memory unit of CPU is a primary memory where data and instruction are stored temporarily. Where as  the processed data and information can be stored in secondary memory permanently so that user can retrieve information whenever required. There are two types of memory used in our computer system.
   1.  Primary memory/Main memory 
   2.  Secondary memory/Auxiliary Memory

1) Primary Memory/Main Memory:

Primary Memory is also known as main memory of computer. This is the place where our data and instruction are stored before processing and the result are stored before displaying output. Memory which stores data and information currently being used by the computer is known as primary memory.

Features of primary memory:

    1. It is not used to store data permanently.

    2. It is usually volatile except ROM.

    3. It is usually expensive and faster than Secondary storage.

    4. It is normally used for smaller storage.

    5. It is not used to transfer data from one computer to another computer.

    6. It is made up of semiconducting material. 

There are two type of Primary memory.

1.1) RAM: RAM stands for Random Access Memory, which stores data and instruction temporarily. It is also known as volatile memory that means data and instruction written in RAM gets erased away when electric power is c.ut off. A user can read as read from it and write in it. Hence, it is also known read-write memory. There are two types of RAM.

SRAM: It stands for Static Random Access Memory. It is made up of transistors. It is called static because it can remember its memory content without being refreshed or as long as there is power. SRAM doesn’t need periodic refreshment like DRAM. It is faster than DRAM but more consume more electricity.

DRAM: It stand for Dynamic Random Access Memory. It is made up of capacitors. It is called dynamic because it needs periodic refreshment and can remember its memory content only after being refreshed as long as there is electric charge in a capacitor. It consume less electricity and is less expensive but is slower than SRAM.

1.2) ROM: ROM stands Read Only Memory where data and information are stored permanently. It is also known as non-volatile memory as data and instruction remain even after there is no power supply. Data are stored in ROM during manufacturing time. The program present in ROM is called firmware and is responsible to boot the computer. The types of ROM are:

PROM: It stands  Programmable Read Only Memory. Initially, it is a blank chip which can be written or program only once by using a special machine called ROM burner. Once the PROM is written it cannot be modified and becomes ROM.

EPROM: It stands  Erasable Programmable Read Only Memory. It is a special chip which can be reprogrammed to recond different information. The data and information are erased by exposing it to the intensive ultra violet light.

EEPROM: It stands for Electrically Erasable Programmable Read Only Memory. This type of chip can be erased and reprogrammed repeatedly with special electric pulses. It doesn’t require special device to write onto it. EEPROM can be re-programmed without removing it from the computer.

2) Secondary Memory/Auxiliary Memory:

Memory which stores data and information permanently for future reference is known as secondary memory. It is a permanent memory where data and instruction remains forever. It is also known as non-volatile memory in which data and instruction remains even if there is no electric supply. This type of memory is also known as auxiliary memory. It has a huge storage capacity up to Gigabytes, Terabytes or even more. Different secondary storage media used are: Magnetic storage, Optical storage and Flash storage.
 2.1) Magnetic Storage: It is a storage media in which data are stored in the form of magnetic spot. A coating of magnetic metal oxide like ferric oxide is done over the disk which attracts the data to be deposited over them. Data are stored in the form of magnetic pattern. Some of the magnetic storage media are: Magnetic tape, Floppy disk and so on.
 Hard disk: It is secondary storage device of  Computer. It is an air-tight sealed consisting of number of magnetic disk (Platters) mounted on a spindle. It was introduced by IBM in 1956 AD. It was first called Winchester disk.Unlike floppy disk it cannot be bend so it is known as hard disk. It is mainly used to store huge volume of data and programs permanently so it is known as non-volatile memory. The disk is divided into the number of concentric circle called tracks and this tracks is divided into invisible segments called sector.

Floppy disk: It is a round and flat disk made up of Mylar (Plastic material) coated with magnetic material. It is read-write memory as we can read from it  as well as write onto it. We can access information from a floppy disk randomly randomly. It has very small storage compare to hard disk.
 2.2) Optical Storage:  is also non-volatile secondary storage media. It is a flat round disk made up of plastic poly carbonate material coated with aluminium alloy. A very fine laser beam is projected to read and write data from and onto the disk. Some commonly used optical storage is CD-ROM, DVD and Blu-Ray (BD). The different types of optical storage are:
 CD-ROM: It stands for Compact Disk- Read Only Memory. It is a optical storage media as it use laser beam to access data from the disk. It can store up to 700mb of data and are useful to store large amount data like computer software, audio, video movies etc. Other types of CD-ROM are CD-R and CD-RW.

DVD: DVD stands for digital Digital Versatile Disk or Digital Video Disk. It is also a type of optical memory which can store very large amount of data and information almost six times more than CD. It is also considered as improved form of CD-ROM and use same technology as that of CD-ROM for reading and writing data.

2.3) Flash Memory:  It is a non-volatile. erasable and programmable solid state memory which is made up of Semi- Conductor chip. It was first introduced in mid 1980’s by Fujio Masuaka in Toshiba Corporation of Japan It can be re-programmed at high speed and hence the name flash. It is derived from EEPROM. In Flash entire memory can be eased in a few second by using electric technolgy. Examples memory card, pen-drive etc.

Classification of computer on the Basis of Size

As we know, technological development and precise engineering had drastically reduce the size of computers. Development of various electronic components are the major cause for reducing the size of the computer. Different types of computer on the basis of size are:

Super Computer: This computer are one of the fastest and powerful digital computer which can perform only a particular types of jobs such as weather forecasting, rocket launching, population counting etc. They were tremendously huge in size and are very expensive. Due to this reason they are not commercially successful. They are used by large corporations and government agencies. They were large in size hence, it occupy much more space and require temperature controlled room.

Mainframe Computer: This computer are also largest, fastest and perhaps one of the most expensive computer. Super computer are much more powerful and expensive but they are similar in size with mainframe computers. These computers have high processing unit and large storage capacity. This computer have multiple terminal. This computer can do big capacity of processing tasks such as population census, agro census, SLC result processing, governmental offices, industries etc. The first computer bought in Nepal in 2028 BS was IBM 1401, which was also a mainframe computer. This computer was bought in Nepal for population counting. Moreover, second computer bought in Nepal was ICL 2950/10 in 2038 BS which was also a mainframe computer brought for same purpose.

Mini Computer:This computer are smaller than mainframe computer and are more powerful and expensive compare with micro-computer. They use terminal and are connected with more than 50 terminal at a time. Hence, it can handle much more amount of input and output than micro computer. The capability of mini computer is somewhere in between mainframe and micro computer. So, they are often called mid-range computer. This computer are used for medium size business, industries, universities, banks due to easy operation than mainframe computer. Eg, Data general, NECK, MAGNUM

Micro Computer: These are the smallest computer develop till date they use micro-processor as their major processing unit. Hence, they are called micro-computers. This computer are small and low cost digital computer. They are also called home computer or personal computer. This days we can find various micro computer that has various processing speed, storage, capacity and size according to cost. They are normally used in office, home, school, shop etc. Micro Computer are also found in various shape and size. They are desktop, Laptop and palmtop.

a. Desktop: They are the personal computer which use micro-processor as a single chip processing unit normally called CPU whose size are so small that they accommodate in a desk of a user. Desktop also have various range of personal computer having several processing speed, storage, capacity and other features. This computer are out popular computer this days. So that, they are used in various commercial field such as school, home, office, business and so on.

b. Laptop: This computer are highly portable micro computers  and can be carried from one place to another easily like briefcase. They are so small that they can be fixed in a lap of a user and hence they are called laptop. They are mostly popular among traveller and the business man. We have to move from one place to another place for work and different reasons. Since, laptop comes with battery backup, we don’t need to have direct A.C. supply. So, we can use without direct connection of electricity. It high reliability, portability and flexibility.

c. Palmtop/Handheld: These are the most portable and smallest device that are develop till date. They are so highly portable that they can be carried easily inside the pocket of the user. Due to small in size they can be adjusted within the palm of the user. So, they are called Palmtop. Several tablets, PDA (Personal Digital Assistant), smartphones are commonly used palmtop these days. This device also gave huge range of application ranging from game playing, internet surfing, and other official needs and requirement. This device also comes with battery backup.

📚EXERCISE

1. Choose the correct option:

a. GIGI refers to the errors due to …….
i. incorrect data ✔
ii. faulty hardware
iv. All of the above
iii. Program

b. ……………. was the main electronic component used in third generation computer.
i. Transistor
ii. Integrated circuit ✔
iii. Vacuum tube
iv. VLSI

c. An analog computer can process …………..
i. temperature
ii. pressure
iii. speed
iv. All of the above ✔

d. In how many generations a computer can be classified?
i. 3
ii. 4
iii. 5 ✔
iv. 6

e. ………. programming language was/were used in first generation computers.
i. Machine language ✔
ii. Assembly language
iii. Both of above
iv. None of above

f. The speed in a supercomputer is measured in ………..
i. Floating point operations per second ✔
ii. Million instructions per second 
iii. Kilobits per second
iv. Gigabits per second

g.  …………. is an input device used on a computer.
i. Microprocessor
ii. Speaker
iii. Touchpad ✔
iv. printer

h. The part of CPU that performs all the processing tasks is known as …………..
i. ROM
ii. RAM
iii. Control Unit
iv. Arithmetic and Logic Unit ✔

i. The CPU performs execution of an instruction in  ………………
i. 3
ii. 4 ✔
iii. 5
iv. 6

j. Which of the following memory is non-volatile memory?
i. Hard disk drive
ii. Optical disk
iii. Pen drive
iv. All of the above ✔

k. The program stored in ROM is called ……..
i. flatware
ii. freeware
iii. formware 
iv. firmware ✔

l. The cache memory is used in a computer to ………
i. store frequently used files
ii. store data and program which are most frequently used by CPU ✔
iii. store the result of processing temporarily
iv. store data and program that a user uses frequently

m. A light sensitive device that converts images or printed document into digital form is …………
i. Plotter
ii. OMR
iii. Scanner ✔
iv. Light Pen

n. A USB refers to ………..
i. storage device
ii. processor
iii. a port type ✔
iv. a serial bus standard

2. Short answer questions:

a. Define a computer. Why is computer known as a versatile and diligent device? Explain.

Ans: A computer is an electronic programmable device that accepts data and instructions, process them and produces information as an output.

A computer is called a versatile device because it has the capability of doing various kinds of tasks. In the same way, a computer can perform tasks repeatedly without loosing speed and accuracy for a long time. So, it is called dilligent device.

b. What are the application areas of computers? Explain in brief.

Ans: A computer can perform different tasks efficiently. So it is used in almost all the fields. Some of the application area of computers are given below:

• Education
• Office
• Banking
• Industry
• Business
• Entertainment.
• Communication
• Health
• Transportation 
• E-Governance

c. Why was the size of the computer reduced in the third generation of computers?

Ans: The size of the computer was reduced in the third generation of Computers because in third generation of Computer Integrated Circuit (IC) was used insted of transistors.

d. Explain the technology used in different generations of computers.

Ans: There are five generations of Computer and in each generation Computers are more advanced and reliable than previous generation because different technologies were used in new generations. All the technology used in different generation of computer are as follows: 
i. First generation Computers = Vaccum Tube
ii. Second generation Computers = Transistor
iii. Third generation Computers =  Integrated Circuit
iv. Fourth generation Computers = LSI and VLSI
v. Fifth generation Computers = Biochips

e. Differentiate between second and third generation computer.

Ans: The differences between second and third generation computers are as follows:

f. What are the different generations of computers? Compare the third generation fourth generation of computers.

Ans: The different generations of computers are as follows:

• First generation Computer
• Second generation Computer
• Third generation Computer
• Fourth generation Computer
• Fifth generation Computer

The differences between third generation and fourth generation computers are as follows:

g. Differentiate between analog and digital computers. 

Ans: The differences between analog and digital computers are as follows:

h. Differentiate between Mini and Mainframe computers.

Ans: The differences between Mini and Mainframe computers are as follows:

i. What is a super computer? Explain its application in a real life situation.

Class 11 Computer Notes

Ans: Super Computer are the most powerful task specific computers which are used by large organisations for scientific and engineering applications where large databases are processed. Some applications of super computer in a real life situation are as follows:

• They are used for weather forecasting.
• They are used for studying earthquake.
• They are used for designing automobiles.

j. What is mobile computing? Explain the importance of mobile computing communication.

Ans: Mobile Computing is a technology that allows the transmission of data, voice and video through a computer or any other wireless enabled devices without having to be connected to a fixed physical link.

Mobile Computing enables people to connect their laptops, tablets etc. to the internet and people can communicate with each from anywhere in the world. It enables people to send emails, audios and videos.

k. What is mobile computing? Explain why it is becoming more popular these days.

Ans: Mobile computing is a technology that allows the transmission of data through any wireless enabled devices. Mobile computing is becoming popular these days because of the following reasons:

• It saves our time.
• It enhance productivity.
• It is a source of entertainment.
• It supports cloud computing.

l. What is a computer system? Explain shortly.

Ans: Computer system is a functional unit in which a group of integrated hardware works together with software to fulfill the purposes of the instructions or program. Basically, it is a system which takes input, process the data and gives meaningful result as an output.

m. Write any five differences between computer organization and computer architecture. 

Ans: The five differences between computer organization and computer architecture are as follows:

n. What is a processing unit? Explain its different components.

Ans: A processing unit is the central processing unit of a computer which carries out the instruction of a computer program by performing basic arithmic and logical operations and controlling different components by sending and receiving control signals. 

The different components of processing unit are as follows :

i. ALU
Arithmetic Logic Unit (ALU) is the part of the CPU where all the processing tasks are actually performed. It performs its entire task according to the control signal from the control unit (CU). As required, data that needs to be processed is transferred from the memory unit to the ALU. During the processing, data may move many times from the memory unit to the ALU and back to the memory unit till the processing is completed. 

ii. CU
Control Unit (CU) is responsible for directing and controlling all the components of the computer including input devices, output devices, memory devices, and other components of the CPU. It uses control signal. The control unit receives instructions from the program, decodes them, and generates signals to inform the ALU and other components about the operation that has been requested. It sends signals to input and output devices to perform tasks as instructed.

iii. MU
A memory unit is a temporary storage area within the CPU that stores instructions and data currently being used in the computer. To execute an instruction, the control unit of the CPU retrieves it from the main memory and places it into a register.  Instructions and data must be in registers before they can be executed or processed. It supplies data to the ALU and stores the results of ALU operations.

o. What is a primary memory? List its functions. 

Ans: Primary memory is the main memory of the computer which stores data and instructions to be used by the Computer temporarily.
The function of Primary memory are as follows:

• It stores all the data to be processed and the instructions ons required for processing.
• It stores currently running program. 
• It stores the intermediate result of processing.

p. How is data processed by a microprocessor? Explain with diagram.

Ans: A microprocessor accepts binary data as input, process the data and then provide output based on the instructions stored in the memory. The data is processed using the microprocessor’s ALU, CU and MU.

The main steps involved in data processing are given below:

i) The control unit sends a virtual address of the data to the protection test unit.

ii) The protection test unit varies the virtual address of the data and forwards the virtual address to the segment and paging Unit, where it is translated into a physical address to be used by the interface unit.

iii) The interface unit locates the address and retrieves the data back through the protection test unit and stores in the internal registers of the CPU. These registers act as the working memory of the execution unit.

iv) If data involves a mathematical calculation, it is sent to the ALU where the calculations are done.

v) Finally, the control unit tells the bus interface unit to send the processed data back to the RAM for storage.

q. What is a system bus? Write the uses of different types of buses.

Ans: A System bus is a facet of computer architecture that transmits and shares data throughout the computer and between devices.

The uses of different types of buses are as follows:

i. Data Bus
It carries the data between the processor and other components. The data bus is bidirectional.

ii. Control Bus 
It carries control signals from the processor to other Components. It also carries the clock’s pulses.

iii. Address Bus 
It carries memory addresses from the processor to other components such as primary storage and input/output devices. The address bus is unidirectional.

r. What is computer memory? Write the differences between SRAM and DRAM.

Ans: A computer memory is  a device or a system used to store information, data and programs that is required for processing. The differences between SRAM and DRAM are as follows:

s. What is cache memory? List its advantages and disadvantages.

Ans: A cache memory is a high speed memory that is built into a CPc which lets you to access data more quickly than you access it from computer hard drive. The advantages and disadvantages of cache memory are as follows:
Advantages
It is faster than main memory.
It consumes the less access time as compared to the main memory.
Disadvantages
It has limited capacity. 
It is very expensive.

t. What is a secondary memory? Why does a computer need secondary storage? Explain.

Ans: A secondary memory is the storage device which stores data, information or programs permanently till they are not deleted.

A computer needs secondary storage device inorder to prevent data and information from being lost when we turn off the computer.

u. What are the differences between HDD and SDD?

Ans: The differences between HDD and SDD are as follows:

v. What is a printer? Write the differences between impact and non-impact printers.

Ans: A printer is an output device that displays the data or result of processing on paper. The differences between impact and non- impact printers are as follows:

w. What is an output? Differentiate between a CRT monitor and a LCD monitor.

Ans: All the devices that are used sed to display or present the result of processing in human-understandable form is known as output device. The differences between a CRT monitor and a LCD monitor are as follows:

x. Write short notes on:

i. Analog Computer 
An analog (also called analogue) computer is a special purpose computer that can process only analog data (continuous varying physical quantities like temperature, pressure, speed, depth, height, voltage, etc.). Analog computers can measure analog data and convert them to numeric value. 

ii. Digital Computer
Digital computers are general purpose computers that can perform a variety of tasks. A digital computer uses the binary digits (bits) 0 and 1 to represent discrete data (discontinuous data) like letters, numbers, symbols, and figures. It can process discrete data. It can perform arithmetic, relational, and logical operations.

iii. Microcomputer
A microcomputer is a digital computer that has a microprocessor as its main electronic component. It is also called a Personal Computer (PC). It is a small and powerful single user computer. It supports many higher level languages, multimedia, graphics, 3D graphics, and games. 

iv. Mainframe Computer
Mainframe computers are multi-user computers that have faster processing speed and more storage capacity than minicomputers. They are capable of handling large volumes of data. Mainframe computers support parallel processing. The parallel processing involves combining a large number of processors that break down an application into many separate parts in order to enhance processing speed. 

v. Supercomputer
Super computers are the most powerful computers. They are the fastest and the most expensive. A supercomputer contains a number of microprocessors that operate in parallel to make it faster. They are task specific computers and are used by large organizations for scientific and engineering applications where large databases are processed. 

vi. Versatility
A computer is a versatile machine. It has the capability of doing various kinds of tasks. Due to the versatile nature of a computer, it is used in almost all fields. It can be used for calculation, preparation of documents, designing, researching, and entertaining. 

vii. Bar Code Reader
A Bar Code Reader (BCR) is an input device that reads the Universal Product Code (UPC) of a bar code and transfers it to a computer. A bar code represents data in a set of vertical parallel lines of varying thicknesses with gaps. Books and goods in the market are labeled with bar codes.

viii. Scanner
A keyboard enables a user to input only text through the different keys. The keyboard cannot input pictures, handwritten or printed documents into a computer. A scanner is an input device that can input any graphical image, photo, handwritten or printed document into a computer.

3. Long answer questions:

a. Explain the features of the computer.

Ans: A computer has different features that are mostly not found on other devices. Some of the main features of Computer are briefly explained below:

i. Automatic
The computer is an automatic machine. Once you have fed instructions to the computer, you don’t need to instruct it again and again. It can do the tasks automatically as instructed by a program.

ii. Storage
Computers can store a large volume of data, information, and programs on storage devices like hard disks, optical disks (CD/DVD/blu-raydiscs) and flash drives as files. These devices store data, information, and programs as long as desired by the user and can be used whenever required. The storage capacities (memory size) of such devices are measured in bytes and higher units of bytes. 

iii. Diligence
Since there are no wearing and tearing parts in a computer, it can perform the task repeatedly without losing speed and accuracy for a long time. Due to this characteristic of a computer, it is also called a diligent machine. This capability of the computer makes it useful in quality control and process control tasks.

iv. Versatility
A computer is a versatile machine. It has the capability of doing various kinds of tasks. Due to the versatile nature of a computer, it is used in almost all fields. It can be used for calculation, preparation of documents, designing, researching, and entertaining. It can even be used for transferring E-Mail, E-Fax, messages and files from one computer to another computer in any part of the world.

v. Reliability
A computer is a reliable and dependable electronic device. The accuracy of a computer is 100%, so a person can rely on the information produced by a computer. A computer stores data and information permanently for future uses. Data and information stored in secondary storage devices do not get deleted till a user does not delete them.

b. Describe the applications of computers in different sectors.

Ans: Computer are widely used in different sectors for different purposes. Some of the application of computer in different sectors are described below:

i. Education
Computers are used in educational institutions like schools, colleges, and universities. In educational institutions, computers are used as teaching aids, information resources, and computing and research tools. For the teaching and learning processes, computers are used by teachers and students in schools and colleges. Computers are also used in the administrative sector for keeping records.

ii. Office
Computers are used in offices to keep records of staffs and prepare different kinds of documents, presentations, spreadsheets, etc. Computers are also used in offices for sending or receiving electronic mails (e-mails). Staffs in offices can also use computers for online chatting. It is used to prepare, store and retrieve data as electronic files.

iii. Banking
Nowadays, almost all banks and finance companies are using computers. Computerized banking system has made banking process faster and easier. Computers have been used in banking sector for the following reasons:

• To control the entire baking system.
• To maintain customers’ accounts. Computers help to calculate payments, interest and balance amount of customers.
• To supervise the entire banking activities.

iv. Desktop Publishing
Computer is essential for Desktop Publishing (DTP). Using Desktop publishing software like Adobe InDesign, Microsoft Publisher, Affinity Publisher, QuarkXPress, VivaDesigner, Scribus, etc. on a computer brochures, magazines, newspapers, books, etc. are designed and produced. The DTP software makes it easy to prepare sketches, images, diagrams and to apply styles and layout texts and graphics. 

c. Explain the advantages and disadvantages of computers.

Ans: The advantages and disadvantages of computers are given below in the form of points.

Advantages of Computer
Computers have had a very vital impact on society. It has changed the way of life of people. The use of computer technology has affected every field of life. People are using computers to perform different tasks quickly, easily, and in a more organized way. Some advantages of computers are:

• It is always accurate and reliable than humans. 
• It is the fastest device and saves our time and money.
• It is a diligence device and can be used regularly for a long time without losing efficiency and accuracy.
• It can be used for communication among many users.
• It is a versatile machine. It can be used in many different areas to do a lot of different tasks.

Disadvantages of Computer
The use of computers has also created some problems in society, which are as follows.

• It reduces the needs of people and increases unemployment in society.
• It has been used for cybercrimes like hacking, creating and spreading viruses, etc. 
• It makes humans fully dependent on it.
• It makes a person non socialization.
• Repair and maintenance are required frequently.

d. Classify the computers in different generations and explain them in shortly.

Ans: Computer are mainly classified into five generations. They are briefly explained below:

i. First Generation Computers
The computers, which were developed from 1943 AD to 1958 AD with vacuum tubes or valves as the main electronic components, are the first generation computers. Due to the vacuum tubes, they were huge, slow, and expensive. They required a lot of electricity and generated a lot of heat.

ii. Second Generation Computers 
All the computers developed from 1959 AD to 1964 AD with transistors as the main electronic component were the second generation computers. In the second generation computers, transistors were used in place of vacuum tubes as the main components in their circuitry. One transistor could do the work of 1000 vacuum tubes. 

iii. Third Generation Computers
The invention of the integrated circuit (I.C.) in 1958 AD by Jack Kilby and Robert Noyce (founder of Intel Company) led to the foundation of third generation computers. The third generation computers appeared in 1965 AD with the I.C., which is also called the ‘Semiconductor Chip’. An IC is a miniaturized electronic circuit that contains a number of transistors ona single wafer of silicon. Due to the use of IC, the third generation computers were more reliable, powerful, and smaller in size.

iv. Fourth Generation Computers 
The fourth generation computers appeared in 1975 AD with microprocessors (i.e. VLSI). The microprocessor or Very Large Scale Integration is an integrated circuit that consists of millions of transistors. The use of microprocessors in computers has made the computers more powerful, efficient, reliable and smaller in size than the computers of previous generations.

v. Fifth Generation Computer 
Fifth generation computers are still in the development stage. The fifth generation computers will be based on biochips or super conductor chips i.e. Ultra Large Scale Integration (ULSI). The fifth generation computers will have artificial intelligence (AI), so they will understand natural language and be capable of thinking themselves. They will have parallel processing capability.

e. Classify the digital computers and explain them.

Ans: Digital computers help users to perform tasks efficiently, conveniently, and in more organized ways. Digital Computer are classified into 4 types which are explained below:

i. Microcomputer
A microcomputer is a digital computer that has a microprocessor as its main electronic component. It is also called a Personal Computer (PC). It is a small and powerful single user computer. It supports many higher level languages, multimedia, graphics, 3D graphics, and games.

ii. Minicomputer
A minicomputer is a general purpose digital computer that can have one or more processors. Minicomputers were developed in 1960s. An early and highly successful minicomputer was PDP-8 which was manufactured by Digital Equipment Corporation (DEC) in 1964 AD. Minicomputers are also known as midrange computers.

iii. Mainframe Computer
Mainframe computers are multi-user computers that have faster processing speed and more storage capacity than minicomputers. They are capable of handling large volumes of data. Mainframe computers support parallel processing. The parallel processing involves combining a large number of processors that break down an application into many separate parts in order to enhance processing speed.

iv. Super Computer
Super computers are the most powerful computers. They are the fastest and the most expensive. A supercomputer contains a number of microprocessors that operate in parallel to make it faster. They are task specific computers and are used by large organizations for scientific and engineering applications where large databases are processed.

f. What is mobile computing? Describe its applications.

Ans: Mobile computing is a technology that allows the transmission of data, voice and videothrough a computer or any other wireless enabled device without having to be connected to a fixed physical link.

Applications of mobile computing Some applications of mobile computing are listed below:

• Email
• Messaging
• Educational services
• Entertainment services
• Web browsing
• E-Commerce 
• Emergency services
• Global position system (GPS)

g. What is a microprocessor? Explain the components of microprocessor.

Ans: A microprocessor is an integrated circuit that contains millions of transistors (i.e. electronic components) packed onto a single chip. It executes instructions of a program, carries out arithmetic and logical operations, and controls other components of a computer. So, it is known as the brain of the computer. The components of computer are as follows:

i. Bus Interface Unit
The Bus Interface Unit (BIU) is the part of the microprocessor that links the CPU with the othe components of a computer. It handles all the transfer of control signals, data and addresses on the buses for the execution unit (EU). It sends out addresses, fetches instructions from memory, reads data from ports and memory, and writes data to ports and memory.

ii. Execution Unit
The execution unit (EU) receives program instruction codes and data from the bus interface unit, executes them, and stores the results in the general registers. It can also store the data in a memory location or send it to an I/O device by passing the data back to the B Since it has no connection with the system buses, it receives and outputs all its data throug BIU.

iii. Prefetch Unit 
The Prefetch unit decides and instructs the bus interface unit to retrieve data and instructions from the main memory (RAM). The prefetch unit queues instructions to assure that the microprocessor is in continuous operation.

iv. Segment and Paging Unit
The segment and paging unit (i.e. memory management unit) converts internal logic addresses into external memory addresses.

v. Decode unit
The decode unit decodes or translates instructions into a simple format understood by the ALU and registers. It makes processing more efficient.

h. What is computer memory? Explain primary and secondary memories.

Ans: Computer memory is a device that stores data, information and programs either temporarily or permanently. Computer memory are classified into primary and secondary memory.

i. Primary Memory
A primary memory is the internal memory of which is also known as main memory. It is a Semi-conductor based computer memory that stores fewer amounts of data. Primary memory is classified into RAM and ROM.

ii. Secondary Memory
A secondary memory is the storage area where information or programs are stored permanently till they are deleted. It is the external memory of the computer which is also known as auxiliary memory.

i. What is a computer system? Explain the components of the computer system.

Ans: A computer system is a functional unit in which a integrated hardware works together with software to fulfill the purpose of instruction or program. The different components of computer system are shortly explained below:

i. Input Unit 
An input unit is the device through which data and instruction are fed in the computer system.

ii. Processing Unit
A processing unit is the central processing unit of computer which process the data entered into the computer by users.

iii. Output Unit 
An output unit is the part of computer system which presents the result of processing and other information.

iv. Storage
A storage is the component of computer system that stores data, information and programs either temporarily for permanently.

j. What is computer architecture and computer organization? Describe the different units of computer system. 

Ans: Computer architecture refers to the conceptual structural design and fundamental operational structure of a computer System. It defines how the different componends of computer system are connected to each other.

Computer Organization refers to the component from which a computer is built. It deals with physical aspect of computer like circuit design, memory and its types etc.

The different units of computer system are as follows:

• Input Unit
• Central Processing Unit
• Memory Unit
• Output Unit

k. Define computer architecture? Draw a block diagram of the computer system along with logical connections. Explain each block in detail.

Ans: Computer architecture refers to the conceptual structural design and fundamental operational structure of a computer system. In other words, it is the conceptual design of different components of a computer system and it defines how the different components of the computer system are connected to each other.

Input Unit
An input unit is a device through which data and instructions are fed into the computer system. It is a medium through which a user communicates with a computer. The input unit converts data and instructions in human understandable form into computer understandable form and passes them to the computer system.

Processing Unit
A processing unit is the central processing unit (CPU) of a computer. The CPU is one of the important components of the computer system. It is also called a processor or microprocessor. It is an integrated circuit containing millions of transistors packed onto a single tiny chip.

Arithmetic Logic Unit (ALU)
Arithmetic Logic Unit (ALU) is the part of the CPU where all the processing tasks are actually performed. It performs its entire task according to the control signal from the control unit (CU). As required, data that needs to be processed is transferred from the memory unit to the ALU.

Control Unit (CU)
Control Unit (CU) is responsible for directing and controlling all the components of the computer including input devices, output devices, memory devices, and other components of the CPU. It uses control signal.

Registers
A register is a temporary storage area within the CPU that stores instructions and data currently being used in the computer. To execute an instruction, the control unit of the CPU retrieves it from the main memory and places it into a register.

Primary Memory 
A computer memory is just like a human brain. It is the part of the computer that stores data, information, instructions, or programs either temporarily or permanently. 

Secondary Memory
A secondary memory or secondary storage device is the storage area where data, information or programs are stored permanently till they are not deleted. It is the external memory of a computer and is also known as auxiliary memory.

Output Units
All the units that are used to display or present the result of processing and other information to the user in a human-understandable form are known as output units. A monitor and a printer are the most commonly used output devices. Some other output devices are speakers, projectors, and plotters.

l.  Explain the role of memory in a computer and differentiate between main memory and auxiliary storage.

Ans: Memory is one of the main requirement of computer system. It is needed for a computer to store, data and instructions.  

The difference between primary memory and auxiliary memory are as follows:

4. Write the full forms of the following:

a. MIPS = Millions Instructions Per Second 
b. GIGO = Garbage In Garbage Out
c. ATM = Automated Teller Machine 
d. SMS = Short Message Service 
e. VOIP = Voice Over Internet Protocol 
f. GPS = Global Positioning System 
g. SSI = Small Scale Integration 
h. MSI = Medium Scale Integration 
i. VLSI = Very Large Scale Integration 
j. ULSI = Ultra Large Scale Integration 
k. BIT = Binary Digits 
l. Al = Artificial Intelligence