Computer Basic Gyan RCSAS Naoholia 2024

Classification of Digital Computer Systems

INTRODUCTION

Computers are classified as Microcomputers Minicomputers, Mainframes and Super computers.

MICROCOMPUTERS

The most familiar kind of computer is the microcomputer. In past, microcomputers have been considered to be of two types - Personal Computers and Workstations. Let use see what these are

Personal Computers (PCs)

Until recently PCs were desktop or portable machines. These machines ran comparatively easy-to-use applications software such as the word processors, spreadsheets etc. They were usually easier to use and more affordable than workstations. However, they had less sophisticated video display screens, operating systems and networking capabilities. Examples of personal computers are Acer's Aspire, Compaq Presario etc.

WORKSTATIONS

Workstations are again, until recently, expensive, powerful machines used by engineers, scientists, other professionals who processed a lot of data. People who need to run complex programs and display both work in progress and results graphically also use workstations. Workstations use sophisticated display screens featuring high-resolution colour graphics and operating system such as UNIX that permitted multitasking. Workstations also use pow erful networking links to mother computers.

MINICOMPUTERS

Minicomputers, also known as mid range computers were first developed as special purpose mainframe computers. They are used, for instance, to control machines in a manufac turing unit. However, now they are widely used as general-purpose computers. Thus the line between minis and mainframes has blurred and is constantly changing Indeed, the more powerful minicomputers models are called Superminis

An example of such a computer architecture is the Client/Server model, in which end users can process at their own microcomputers. End users can also access and share the resources of the server, which usually is a minicomputer.

MAINFRAMES

Mainframe computers can process several million-program instructions per second. Large organizations rely on these room-size system to handle large program with lots of data. Main- frames are mainly used by insurance companies, banks, airline and railway reservation sys tem, etc. An advanced mainframe made by IBM is S/390

SUPERCOMPUTERS

Supercomputers are the fastest calculating devices ever invented. A desktop microcomputer processes data and instructions in millons of second, or microseconds. A supercomputers. by constrast, can operate at speeds measured in nanoseconds and even in picoseconds one thousand to one million times as fast as microcomputers.

Most supercomputers are used by government agencies. These machines are for applications requiring very large programs and huge amounts of data that must be processed quickly Examples of such task are weather forecasting, oil exploration, weapons research, and large scale simulation. The cheif difference between a supercomputer and a mainframe is that a supercomputer channels all its power into executing a few programs as fast as possible.

whereas a mainfiame uses its power to execute many programs concurrently

Characteristics of Computer

There are certain features, which has made computer an indispensable element in the proper functioning of our life.

Speed

Computers works at a very high speed. It can perform any work within its defined scope in a few seconds, as compared to human.

Accuracy

Computers hardly makes any mistakes. There is a high consistency of accuracy within computers. Errors do occur in a computer, but due to human negligence.

Diligence

Computers can perform all day long tong resulting in quality output. The reason is it does not get tired or bored as any other human being. Thus the monotony of work does not effect computers.

Versatile

Computers can perform all types of taska, depending on its scope. It can range from desigining a dress to that of desigining nuclear weapons. Hence it is regarded versatile.

Memory

Computers can store and recall any armount of data whenever required. It depends upon the user to decide which information is required and is stored in the secondary storage device for later use. The Information is real and accurate, which is not pomible for a human brain.

Binary Number System

The binary mumber system is similar to decimal system, but the base is two. Two symbols or digits O and I are used in this nuniber system. Each position in a binary mumber representa a power of base 2. Binary digits is often referred to as bit. Thus a bit means either 0 and 1. A binary namber consisting of number bits is called-binary numbers. The data, mumbers, letters and other special chanacters are stored in the form of binary system.

Characteristics

A positional number system

Has only 2 symbols or digits (0 and 1). Hence its base-2 The maximum value of a single digit in 1 (one less than the value of the base) Each position of a digit represents a specific power of the base (2) This number system is used in computers Anatomy of a Digital Computer FUNCTIONS AND COMPONENTS OF A COMPUTER

To function properly, the computer noods both hardware and software. Hardware consists of the mechanical and electronics devices, which we can see and touch. The software consists of programs, the operating system and the data that reside in the memory and storage devices.

nal A computer does mainly the following four functices

bit

Receive input-

Acuept infirmation from outside through various input devices like the keyboard, mouse etc.

Process information-Perform arithmetic or logical opentions on the information.

Produce output-

Communicate Information to the outside world thugh output devices like monitor, printer etc

Store information

Store the information in storage devices like hard disk, floppy diskes ete

CENTRAL PROCESSING UNIT (CPU)

The part of the computer that execute program instruction is known as the Processor at Central Processing Unit (CPU). In a microcomputer, the CPU is on a single electronic component, the micropescessor chip, within the system unit or system cabinet. The system unit also includes circuit boards, memory chips, porta and other components

The CPU las two parts-the Control Unit and the Arithermatic Logic Unit (ALU). In aminoproosser, bothare on the microprocessor chip.

Control Unit

The control unit tells the rest of the computer system how to carry out a program's instructions. It directa the movement of the electronic signals between memory-which temporarily holdy data, instructions and processed information and the ALU. It also directs these control signals between the CPU and the input output devices

Arithmetic Logic Unit (ALU)

Arithmetic-Logic Unit, usually called the ALU, performs two types of operations arithmetic and logical. Arithmetic operations are the fundamental mathematical operations consisting of addition, subtraction, multiplication and division. Logical openstions comists ofcomparation. That is, two pieces of datuare compared to see whether one is equal to, less than, or greater than the other MEMORY

Memory-also known as the primary storage or main memory - is a part of the microcomputer that hold data for processing, instruction for processing the data (the progmm) and information (processed data)

Registers

The main function of a CPL is to interpeet and execute instructions. This involves a movement of data within various units of a computer system. To carry a smooth and faster procesos of transferting data, a number of special memory unit known as registers are used in computer system. The registers do not form a part of the memory and the data are stored imponrily. There are different types of registers, which can be closifled according to the function.

No

Name of the register Memory Address (MAR)

Function

To hold the address of the active location.

To hold the information on its way to and from memory. To hold the address of the next instruction to he

executed

To accumalate result and data to be executed To hold an instruction while it is being executed. To communicate with the input/output devices

4

Memory Buffer (MBR) Progrum Control (PC)

Accumulator (A)

Instruction ()

6 Input/Output (1/0)

Memory Units

INTRODUCTION

Memory units are the intemal storage areas in a computer. The term "wemory"indentifies data stornuge that comes in the form of chips and the word "storage" is used for memory that exists on tapes or diska, Moreover, the term memory is usually used as a short form for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk

Every computer comes with a certain amount of physical memory, usually referred to as the main memory or RAM. You can think of the main memory as an array of bones ench of which can hold a single byte of information. A computer that has I megabyte of memory, therefore can hold about 1 million bytes (or characters) of information.

There are several types of memory

RAM (Random Access Memory): This is the same as the main memory, When use by itself, the term RAM refers to read and write that is, you can both write data inte RAM and read data from RAM. This is in constrast to ROM, which permits you only to read dats. Most RAM is volatile, which means that it requines a steady flow of electricity to maintain ita contents. As soon as the power is turned off, whatavce data war in RAM is lost.

ROM (Read Only Memory): Computers slimost contain a still amount of a d-only memory that holds instruction for starting up the computers. Unlike RAM, ROM cannnot be written to.

PROM (Programmable Read-Only Memory): A PROM is memory chip on which you can stor a program. But once the PROM has been used, you canoot wige in elaun und use it to sto something ebe La ROM, PROMs an non-volatile.

EPROM(Erasable Programmable Read-Only Memory): An EPROM is a special type of PROM that can be eraand by exposing it to ultraviolett

EEPROM(Electrically Erasable Programmable Read-Only Memory): An EEPROM is a special typeof PROM that can be ersed by exposing into an electrical charge

FLASH MEMORY

Flash momnory is a special type of EEPROM that can be enooid and reprogrammed in blocka inseal of ano bytu at a tima. Many modems PCs have their B05 (Basic Input Output System) atured on a flash memory chip so that it can easily he updated if necery Such a BOS is sometimes callest a flash Bos Flash memory is also popular in modenna because it enables the modern manufacturer to support.nrw protocals as they become standardized.

Auxillary Storage Devices

INTRODUCTION

Auxilary storage also known as anlary memory or secondmy stomge, is the memory that supplements the main semge. This a long-terms, noe-volatile memory. The tams non-volatile mears it stores and stains the programs and data even after the computer is switched off. The most common types of auxilary storage devices are magneóc tapes, magnetic disko, floppy diska, hard disks, etc.

There are two types of auxilary storage devices. This classification is based on the type of data access noqumtial access media and random-medis. In the case of sequential-access medis, the data storted in the media can only be nad in sequmor and to get to a particular point on the media you have to go through all the precoding points,

Few Terms related to Memory Measurement in Computers:

When you me a RAM, ROM, Floppy disk or hard disk, the data is measured using some malt. In Com puter terminology, they are called Nibble, Bà, Byte, Kilobyte, Megabyte, Gigabyte etc.

Be It stands for a Binary Digit, which is either 0 or 1.

8 bits is called a bytz.

Byte (28) a byte is appron imately one charuour eg letter's, number symbol "" etc. Also a group of

Nibble 4 bits make one nibble.

Kilobyte (KB) la mamery, a group of 1024 bytes is called a kilobyte.

Megalete (MM) A group of 1024 kilobytes in colled a Megayte. It is sometimes used, less precisely to mean I million bytes of 1000 KB

Input Devices

INTRODUCTION

An input device is any machine that feeds data into a computer. For example, a keyboard is an input device, whereas a display monitor is an output device. Input devices other than the keyboard are sometimes called alternate input device. Mice, trackballs and light pens are all alternate input devices.

KEYBOARD

Keyboard is an input device consisting of a set of typewriter - like keys that enables us to enter data into a computer. Computer keyboards are similar to electric typewriter keyboards but contain additional keys. The keys are often classified as follows:

Alphanumeric keys - letters and numbers.

Punctuation keys-comma, period, semicolon and so-on

Special keys

function keys, control keys, arrow keys, Caps Lock Key and so-on

Light pen

This is a stylus with a light sensitive tip that is used to draw directly on a computeris video screen or to select information on the screen by pressing a clip in the light pen or by pressing the light pen against the surface of the screen. The pen contains light sensors that identify which portion of the screen it is passed over. It is mostly used with Laptop.

Microphone

This is a device for converting sound into signals that can then be stored, manipulated, and played back by the computer. A voice recognition module is a device that converts spoken words into information that the computer can recognize and process.

MOUSE

Mouse is a device that controls the movement of the cursor or pointer on a display screen. A mouse is a small object you can roll along a hard surface. Its name is derieved from its shape, which looks a bit like a mouse, its connecting wire that one can imagine to be the mouse's tail, and the fact that one must make it scurry along a surface. As you move the mouse, the pointer on the display screen moves in the same direction. Mice contain at least one button and sometimes as many as three, which have different functions depending on what program is running.

Types of Mice

There are three basic types of mice Mechanical has a rubber or metal ball on its underside that can roll in all directions. Mechanical sensors within the mouse detect the direction the ball is rolling and move the screen pointer accordingly.

Optomechanical Same as mechanical mouse, but uses optical sensors to detect motion of the ball.

Optical uses a laser to detect the mouse movement. You must move the mouse along a special mat with a grid so that the optical mechanism has a frame of reference. Optical mice have no mechanical moving parts. They responds more quickly and precisely than mechanical and optomechanical mice, but they are also more expensive.

Scanners

Scanners are used for direct data entry into the computer system and are capable of recognized marks or characters. Situations might arise when some image that is available on paper is required for further editing on the computer disk. The easiest way out would be to take a photograph of the image directly from the source, and scan it and save it on the disk. If required print out can be taken. Scanners are used for scanning text and graphics files together.

A scanner scans an image and transform the image to the code that is used by the computer to represent the characters of the keyboard. These can be edited, manipulated and printed.

Sacnners are of two types: the flat-bed type and the roller feed type. While in a roller feed scanner, the image is passed over a roller when it is captured. The flat bed works like a photocopier.

Output Devices

INTRODUCTION

Output is anything that cotes of a compster. Output can be meaningful information or gibberish, and it appear in a variety of flems a binary numbers, as characters, as pictures, and as printed pages.

An output device is any machine capable of representing information from a computer. Output devi include display screen, loudspeakers, printers, ploters, etc.

MONITOR

Monitor is another tem for the display screen. The term monitor, however, usually refliers to the entire box whereas display screen can muun just the screen. In addition, the tam monitor often implies graphies capabilities.

CLASSIFICATION OF MONITORS-BASED COLOUR

There are many ways to clamify monitors. monhors into theve classes Monochrome The most hasic is in term of colour capabilities, which separates

Monochrome monitors actually display two colours, one for the background and one for the foreground. The colours can be black and white, green and black, or amber and black,

Grav-scale

A Gray-scale is a special type of monochrome monitor capable of displaying different shades of gmy.

Colour

Colour monitors can display anywhere from 16 to over 1 millon different colours. Colour monitors an sometimes called RGB monitors because they accept three separate signah-red, green, and blue. This differs from colour television, for mample, which use componite video signals, in which all the colours are mixed together. All colour computers are RGB monitors.

Refresh Rate

Display monitors must be refreshed many times per second. The refresh rate determines how many times per second the screen is to be refreshed (redrawn). The refresh rate for a monitor is measured in hertz (ht) and is to also called the vertical frequency or vertical refresh rate. The old standard for monitor refresh rates was 60hz, but a new standard developed by VESA sets the refresh rate at 75 hz for VGA and SOVA monitors. The faster the refresh rate, the less the monitors flickers.

Printer

The output generated in the VDU cannot be stored for permanent use. Printers are the most widely used output devices. Print out can be taken for permanent use. There are several types of printers that am classified depending on speed, cost and the quality of the printing. They are as follows:

a. Character printer

b. Line printer

c. Page or Lacer printer

Character Printer

These type of printers print one character at a time, Example is typewriter. Two types of pristers full

under this category. 1) Dot Matrix Printers

Each character as printed out appears as a pattern of dots. The print head is comprised of a matrix of tiny noalles. They do not have any fixed tint. The print quality is infirior to that of deiny wheel printer but is much faster. The speed ninges from 40 to 250 characters per seconds.

2) Ink Jet Printers

Based on new technology, these printers are non impact character printem. Small amount of ink is sprayed onto the paper to print the characters. The ink contains high amount of iron. It can pelet any character of any size and shape and also different coloured irika can be used.

Line Printers

These printers are impact peinters and used with most medium and large computer systems for producing voluminous print outs. Generally these printers have a speed of printing 300 to 2500 per minde. There are twe important printers that can be grouped under this category.

Drum Printer

The printer is a solid, cylindrical drum like structure that accepts characters in bends on its surface The number of bands is equal to the number of printing positions. All the possible characters to be printed are contained by each band. This spend of drum printer range from 300 2000 lines per minutes

Chain Printer

This printer use a fast moving chain called o print chain. Fach link of the chain isa character font. Tit enhance the speed of this printers, characters set goes on repenting. The speed of these printers mnge from 400 to 2500 characters per minutes.

Page or Leser Printers The printer falling under this category are non-impact printers. They have a very high speed of over 20000 thousand lines per minutes. This has bem pomible by using electro-photographic technique As it is so efficient where thousands of pages can be printed at a time, it cannot be used in small concem as it is too expensive.

Plotter

Another output device, plotter is used to produce hed copies of graph and design. There are basically two types of plotter-drum and flatbed. In case of drum plotter, the paper to be designed is placed on the drum and a vertical motion is produced when the drum moves to the front to back. Also pes with different inks can be used. A flatted plotter plots on papers that are spread and fised over a rectangular flatbed table similarly like the photocopior. The area is fixed as that of the plot size. Plotters now in the market are used with personal computers. This are generally very slow as a lot of mechinical movement is involved in the process.

Introduction to software

What is software?

A computer cannot perform on its own. It needs to be execlusively instructed on what it has to do. A set of instruction written in computer language is known as program and two or more programs are known as software. The main objective of software is to enhance the capabilities of the computer.

Classification of software

Computer software is generally classified into two broad categories

1. System software.

2. Application software.

Application software

This software is also known as application package. It is a set of one or more programs designed to carry out specific operation depending on the application. The program that constitute an application package are known as application software. As there has been the expansion of the software industry many application packages have been developed in the field of banking, insurance, medicine, manufacturing, designing, entertainment and so on.

System software

This software is also known as system package. It is a set of one or more programs, designed to control the operation of a computer system. The system package are not meant for solving specific problems. Generally, the system packages support the running of the other software, communicate with other peripheral devices, support the development of other type of software and supervise the use of various hardware resources. Without system software, application software could not be run on the computer system. System programmers design the system packages. It is an indispensible part of a total computer system.

Complier, Assembler and Interpreter

Complier, Assemblers, and Interpreters belong to systems software to translate a source program to an object program. These translators are known as assembler language processors. They are used for processing language.

Operating System

What is an Operating System?

The Operating System (OS) is an integrated set of program that is used to manage the various resources and overall operations of a computer system. Its prime objectives is to improve the performance and efficiency of a computer system. The operating system is responsible for the smooth and efficient operation of the entire computer system. The memory, disk space, processor time, and peripheral devices such as keyboard, mouse, monitors, printers, modems, etc. that are required by a computer system are provided by the operating system.

Evolution of Operating System

The main aim behind the evolution of operating system was to use the computer system in the most efficient and economic way.

In early days the function of the operating system was to clear the main memory to remove any data remaining from the previous job, then load the next program and data from the input devices, set the appropiate switches and finally run the job to obtain the results from the output devices. The same process was repeated for other jobs, which involved a lot of time.

A new method of automatic job-to-job transition was designed. The operating system reduced the idle time of the computer system. But the CPU time also needed some enhancements. More than one program was run at a time, that is while one program carries out the input output operation, the CPU was involved in another operation.

Functions of an Operating System

The operating system perform the following functions:

Processor Management: It is the operating system that allocates processor time to complete

the tasks as being performed by the computer system.

Memory Management: Primary Memory and other storage devices are to be assigned to the system programs as well as the user program and input, which are done by the operating system.

Input/Output Management: In cases where different programs are running, various input and output are generated which is kept track by the operating system.

File Management: The storing and transferring of files from a storage device to another includes within the tasks list of the operating system.

Priority Management: A computer is desired to do things a lot of jobs at one time. It is the operating system which determines which needs to be executed first.

Switching between programs: Various applications can be run at a time. The switching over from an application to another is also the tasks of operating system.

Interpretation: Computer only understands machine language in the form of electrical signals. To make any application run, the commands has to be interpreted by the operating system and send for processing and once the output is generated it has to be transferred to readable language.

Co-ordination and assignment of software: There are software such as complier, assembler and utility programs needed for a user computer. Operating system allocates all these software.

DATA COMMUNICATION AND COMPUTER NETWORKS

What is the meaning of Data Communication?

Communication is the process of sending and recieving information from one person to another. This process involves three basic components: the sender, who is sending the information, amedia, to carry the information and the reciever, who accepts the information. For example, Mr. A is the sender, Mr. B is the reciever and the media used is the phone line

The same phenomenon is followed by the data communications. The exception in this case is that the sender and the reciever usually are computers. The transmission can include telephone line, mtellite linio, microwave link etc, where the data tumains unchanged.

Different types of Data Transmission Modes

Duta can be transfered from one computer to another using one of the following modes

Simplex

Half-duplex

Full-duplex

Simplex

This type of data communication takes palce in one direction. The informatine flow is unidirectional. This meses data can be send from one point only. As this type of communication is limited, it is mrely used,

Half-Duples

This type of communication can transfer dan in both directions, but one direction at a time. Two-wires are required, as alternatively data can be send and recieved. Generally this type of method is used to conttect a computer with a terminal

Fall-Duplex

This type of data communication allows simultanoous transmission of data in both directions. It improves efficiency of sending and receiving data in a much faster way. Four wires are required in this type of transmision.

Windows

Introduction to Windows

Windows is an operating system, offer a variety of facilities to develop application, manage compute resources with case and to use the cortiputer efficiently. From the seventies when GUI (Graphical User Interface) emcept was developed though early and mid eighties to the real development of GUI to the mid and late nineties with the capacity of virtual offects (eye binding). Uhimately opening new doors inte the new milleniarn the windows has evolutionised in a long way from a single GUI. But revolutionary software application to the self complete multi programming, multi user operating system, inflict with extra edges to control the whole system of software and handware under the control of user as a common platform for all. It is highly user friendly and mables the user to work with pictures or icons. The user doesn't has to remember commands as it DOS. It is a graphical system or graphical user interface humed kyntem and has been popular among the computer users as its learning period is very less

The windows gives a pictorial representations of the command (operation). The pictorial representation is sometimes called Icon or buttons. In order to execute the operation, the user has to choose (chick) the appropriate bution with the help of some pointing description like the mune. Any query or mpersentation on the screen will be in a rectangular arcu called windows. Each operation appears in a window. This window can be moved or resized. In windows enviroment multiple programs can be seon on the screen at a time. This features of windows is known as multitasking whereas DOS doesn't supports multitasking. In windows also the system of maintaining files and directories are the same as in DOS. The only difference is that windows file and directories nune can be upto 256 characters long. And the directories are called as folders instead of directorias

Windows is a boon for users of DOS. They no longer need to understand the comples syntax of DOS commands. Windows provides a standard, user friendly, powerful interface for all programs under DOS

Types of Windows

There are two types of windows

Application Windows: These windows contain a program that you are running and working with, wach as Microsoft Word, Excel, Power-Point etc. Most of the work that you will do will be on application window

Document Windows: Some programs are designed in such away that it will allow you to work on mam than one document that open at a time. For campixe Microsoft word for windows allows you to have several documents open at once, in a separate document window. Instead of running "word" several times (which will use up too much precious RAM ), in separate application windows, you can nan it in one application and open several document windows within the main application windows.

Parts of a Window:

Most windows have certain components in correnon. Because of these sinihrition, nearly all windoves can be operated in the same manisse. The parts of a window are:

Tile barst The name of the program or document appears at the top of each respective window, which is called the title har. The title title bar bar also serves another function, it indicates which window is active window. Active window is the one you am cuarently working in. When a window is made active, it janga to the front of other windows that might be obscuring it and its title bur change colour. You can make a window active by clicking unywhere within its berder:

Minimize, Maximire/Restore and Close button: Thure are three buttons at the right end of the title bar with small graphics in then. These are little control butons with which you can quickly charge the size ofa windone

Note: After a window has been mas tmised, the simized button change to mitore button