BSc. Solutions and Notes: Unit-1 : Introduction to Computer (Notes of TU Bsc. 4th Year Computer Science)

Introduction to Computer

Syllabus: Definition and Characteristics of Computer; Evolution and Generations of Computers in Brief; Classification of Computers (Super, Mainframe, Mini and Microcomputer; Analog, Digital, and Hybrid Computer); Basic Computer Organization (Input, Output, and Memory/Storage Unit; Central Processing Unit); Computer Software (Definition of Software, System Software, and Application Software)

The computer is an electronic data processing device that accepts and stores data input, processes the data input, and generates the output in a required format.

Computers can access and process data millions of times faster than human beings. It can do a lot of tasks such as playing games, railways, reservations, weather forecasting, error detection, etc. A useable computer is a combination of hardware, software, and users.

Characteristics of Computer

High speed: The computer is a very fast device. It has units of speed in a microsecond, nanosecond, and even the picoseconds. It can perform millions of calculations in a few seconds.
Accuracy: They are accurate. The calculations are 100% error-free. It gives false results only when the wrong data is entered. This is known as GIGO ( Garbage In Garbage Out).
Storage Capacity: Storage is a very important characteristic of computers. It can store large amounts of data. At present, hard disks are available in hundreds of GigaBytes (GB).
Diligence: Unlike human beings, a computer is free from monotony, tiredness, and lack of concentration. It can do repeated work with the same speed and accuracy.
Versatility: A computer is a versatile machine capable of performing all kinds of tasks. A computer is very flexible in performing the jobs to be done.
Automatic: As it is an automatic machine. Once data and programs are given to the computer and stored in computer memory, the program and instruction can control the program execution without human interaction.
Reliability: It is a reliable machine. Computers are designed to make maintenance easy.
No IQ: A computer is a machine that has no intelligence to perform any task or we can say it cannot take decisions on its own.
No feeling: It has no feeling or emotions.

Generation of Computer

Generation in computer terminology is a change in technology a computer is/was being used.

There are totally five computer generations known to date.

First Generation Computer (1946-1959)

It used vacuum tubes as the memory device.
They were huge in size and expensive.
Their operating speed was unto millisecond.
They used machine level language.
ENIAC, Mark-I, and EDVAC are first-generation computers.

Advantages:

Vacuum tubes were the only electronic components available during those days.
It made possible the advent of electronic digital computers.

Disadvantages:

Too bulky in size so not portable.
Very unreliable because prone to hardware failures.
Commercial production was difficult and costly so limited to commercial use.

Second Generation Computer (1959-1965)

They used transistors as the main components.
They used magnetic disk as secondary storage.
Operating speed was increased.
They were smaller and cheaper.
Used magnetic core memory for internal storage.
IBM 1401 and ICL 1300 were a second-generation computers.

Advantages:

Smaller in size and have better portability.
More reliable than the first-generation computer.
Generate less heat and hence can be operated for longer times.
Wider commercial use.

Disadvantages:

Air conditioning is still required.
Commercial production was difficult and costly.

Third Generation Computer (1965-1971)

They used Integrated Chip (IC) as a memory device.
The operating speed was increased unto nanosecond.
They support high-level language.
Used a semiconductor device as primary storage.
IBM 360, ICI-1901, etc. are third-generation computers.

Advantages:

Smaller in size as compared to the previous generation thus have increased portability.
More reliable.
Less power requirement.
Commercial production was easier.

Disadvantages:

Air conditioning required in many cases.
Highly sophisticated technology is required for the manufacture of IC chips.

Fourth Generation Computer (1971-1980)

They used microchips (VLSI) as the memory device.
Size of the computer reduced to desktop, laptop, and notebook.
Used object-oriented programming language.
Speed was increased up to picoseconds.

Advantages:

Smallest in size and portable.
Very reliable and heat generated is negligible.
No air conditioning required in most cases.
Much faster and cheapest among all generations.

Disadvantages:

Highly sophisticated technology required for the manufacture of VISI chips.

Fifth Generation Computer (1980-future)

Biochip will be used as the main component.
They will have artificial intelligence.
They will provide a natural computer interface.
They will use a multi/parallel processor system.

Classification of Computer

They are generally classified on the basis of size and power and on the basis of the working principle.

On the Basis of Working Principal

We can classify into three types on this basis.

Analog computer - An analog computer is a special purpose computer. It can measure physical value (i.e. continuous flow of data) like the voltage, current, temperature, pressure, etc. All operations in the analog computer are performed in parallel. Analog computers are used for scientific and engineering purposes. Examples of analog computers are (i) speedometer in car or motorcycle (ii) thermometer (iii) seismograph that measures earthquake.

Digital computer - Digital computers are general-purpose computers. They use discrete data like letters, numbers, symbols. They represent discrete data in binary digits either 0 or 1. Digital computers work on binary digits. All operations in the digital computer are performed sequentially, one step at a time. They are mostly used in different sectors for performing a variety of tasks.

Hybrid computers - Hybrid computers are special-purpose computers. They have the capabilities of both analog computers and digital computers. Hybrid computers can accept input in analog form, process data digitally and provide output in either digital or analog form. They are used in industrial applications, airplanes, ships, hospitals, and scientific research centers. Eg. ECG, halter monitoring machine, ultrasound machine, CT-scan machine, etc.

On the Basis of Power and Size

Supercomputer: One of the fastest computers currently available. They are very expensive and are employed for specializing applications that require an immense amount of mathematical calculations. It consists of thousands of integrated microprocessors for parallel processing. Example : Cray-1, ETA10, etc.
Mainframe computer: They are very large in size and expensive. They are capable of supporting thousands of users simultaneously. It is mainly used by insurance companies, banks, airlines, ticket reservations, etc. Example: IBM360, IBM370, etc.
Minicomputer: They are multiprocessing and mid-sized computers. They can perform several actions at the same time and can support unto 25 users. It is less powerful than the mainframe and supercomputer but more powerful than a microcomputer.
Microcomputer/personal computer: It is defined as a small, relatively cheap computer designed for an individual user. It is based on microprocessor technology. The peripheral devices used in microcomputers are keyboard, magnetic disk, monitor, etc.

Computer System

Major hardware components in computer systems are:

Central Processing Unit (CPU) - The part of the computer that executes programs, instructions is known as processor or CPU. It consists of three components which are:
a) Arithmetic Logic Unit (ALU) which performs fundamental mathematical operations.
b) Control Unit (CU) which coordinates and controls the operation of a computer system.
c) Register are high-speed storage areas in the CPU that store very small amounts of data and instructions.
Input Unit - A device that is used to feed data into a computer is called the input divide or input unit. It sends data into the CPU or RAM. There are different types of input devices. Some common input devices are keyboard, mouse, scanner, lightpen, etc.
Output Unit - Any device that receives and displays output from a computer is called an output device or output unit. It is also defined as any piece of computer hardware equipment used to communicate the results of a computer to the outside work. Some examples are monitor, printer, plotter, speaker, etc.
Memory/Storage Unit - Memory unit is used to store data, information, and instructions for computer. Without memory units, computers can’t even start up as information stored in the memory unit is responsible for computer operations. Primary memory and secondary memory are two components of the memory unit.

Differences between Primary Memory and Secondary Memory

Primary Memory	Secondary Memory
A memory that is accessible directly by the processing unit is called primary memory.	The memory or storage device that is not directly accessible to CPU is called secondary memory.
Normally volatile in nature. Content is lost when power is lost.	Normally nonvolatile in nature.
Used to store program instructions and data that are used during current execution.	Used to hold programs and all data needed by the program on a permanent basis.
Faster than secondary memory.	Slower than primary memory.
Expensive	Cheap
Accessible to CPU directly	Cannot be accessed
Example: RAM, ROM, etc.	Example: Hard disk, Flash memory, etc.

Software

Software is a logical component of a computer system that are logically available, logical behavior, and intangible in nature.

A set of programs, booting procedure and associate documentation related to the effective operation of a computer system are termed as software. There are 2 types of software,

System software
Application software

System Software:

It is the collection of programs designed to operate, control, and manage the actual operation of the computer equipment. It is developed by manufacturers to provide software tools that enable the user to write and run application software.

System software supports the following,

Running of other programs
Supports the development of other application software
Development of other types of software
Maintaining other various hardware resources

There are 3 types of operating software:

Operating System - It is an integrated set of a specialized program that is used to manage the resource and overall operations of the computer. It acts as the mediator between hardware and computer application programs. It manages all the resources of a computer system. It makes the computer easier to use and allows an efficient and fair sharing of system software.
Language Processor - Programs or software which translate instructions written in human convenient form to machine language code is called language processor. The program translated by the language processor is understood by the hardware of the computer system.
Utility Software - A program that performs a very specific task usually related to managing system resources is called utility software. Example: antivirus, backup, etc.

2) Application Software:

They are a set of one or more programs designed to carry operations for specified applications directly to the users. It helps the users to work faster, more efficiently, and more productively.

There are 3 types of application software,

Tailored Software - Software specially designed to meet the specific requirement of an organization or individuals. As a tailor measures the dimension of a person for sewing clothes, a tailored software is written on the demand of individual need and serve only one user.
Package Software - General set of program that allows the computer to perform the specific data processing job for users.

Application Software	System Software
It is a user-oriented software.	It is a hardware-oriented software.
It is developed to solve a particular problem.	It is developed to operate or manage the hardware components.
It is usually not provided by the hardware developer, a user has to add as per need.	It is usually provided by the hardware developer along with the hardware.
It is usually expensive.	It is either cheaper or provided free of cost.
A computer runs without application software.	A computer cannot be operated without system software.
It is comparatively easier to develop.	It is difficult to develop and require high-level intelligence.
Application software can be developed without knowledge of computer hardware.	To develop system software, the user should have a deep knowledge of computer hardware.
Eg. MS Office package, Tally, Banking.	Eg. MS Windows, Android, Device driver.