Introduction
The word ‘Computer’ comes from the Latin word ‘Computerae’ mean ing to compute. Com puter is de fined as
“An automatic electronic apparatus for making calculationsor controlling operations that are
expressible in numerical or logical terms”.
Some Important Terms Related to Computer
Data The word data has been derived from Latin word ‘datum’ (Means facts). It is a collection of facts
and figures which are not in directly usable form.
Processing The act of performing some actions to convert into useful form.
Information It is processed data or final result which is in directly usable form and conveys some
meaningful results.
Instruction It is type of action to be taken on data.
Basic Operations Input, Storing, Processing, Output, Control.
Components of a Computer
Input Unit
l It accepts data and instructions from the user.
l It converts the accepted instructions into the machine language.
l It gives converted instructions to CPU for processing.
eg, Key board, Mouse, Light Pen, Joystick, Mag netic Ball, OCR (Op ti cal Char ac ter Reader), Floppy Disk
Drive, Mag netic Disk Drive, Bar Code Reader, Smart Card Reader, Bio met ric Sen sor, Touch Screen, Punched
Card Reader, Sty lus and Tab let, Puck or Mi cro phone, Dig i tal Cam era, Scanner, etc.
Central Processing Unit (CPU)
l All processing work of computer is performed by it.
l It is also termed as brain of computer.
l It controls all the parts of computer system.
It is further classified into three components
(a) Arith me tic and Logic Unit It per forms all arith me tic and logic op er a tions. It con sists of num ber of
small lo ca tions, termed as reg is ters. It has two parts (i) Arith me tic Sec tion All com plex arith me tic ex pres sions are per formed by re pet i tive com bi na tion of
these op er a tions.
(ii) Logic Sec tion It performs all logic op er a tions like com par ing, se lect ing and merg ing of data.
(b) Control Unit It gives com mand to trans fer data from the in put de vices to mem ory and from mem ory to
arith me tic logic unit. It trans fers the re sults from mem ory to out put unit.
(c) Memory It temporarily (Primary) / permanently (Secondary) holds the data received from input device.
It holds the data being processed and intermediate results being generated. It holds the system software
and the application software in use.
It can be classified into two types
RAM (Ran dom Ac cess Mem ory) RAM is where all ac tive pro grams and data are stored so that they are
readily avail able and eas ily ac cessed by the CPU.
ROM (Read Only Mem ory) It is log i cal then that data stored on ROM can not be changed. It is non vol a tile
which means that it can keep its con tents even with out a power source.
l PROM (Programmable Read Only Memory)
l EPROM (Erasable Programmable Read Only Memory)
l EEPROM (Electrically Erasable Programmable Read Only Memory)
Output Unit
It accepts processed data (results) from CPU.
It converts results from machine language into some simple language.
It displays results to user.
eg, Vi sual Dis play Unit (VDU), Printer, Plot ter, Floppy Disk Drive, Mag netic Disk Drive, Speaker, Pen
Drive, etc.
Software It is a set of in struc tions that di rects the com puter to pro cess in for ma tion. It can be clas si fied
into three types
(i) System Software It co or di nates the op er a tion of the var i ous hard ware com po nents of the com puter. eg,
MS DOS, Win dows 95/98/2000/XP/Vista, Linux and UNIX.
(ii) Ap pli ca tion Soft ware It is a set of pro gram de signed for spe cific uses or applications eg, MS Word,
MS Ex cel etc.
(iii) Util i ties Soft ware Util ity pro grams are those that are very of ten re quested by many ap pli ca tion
pro grams. It is used to de bug the soft ware er rors, cor rect the data through the ed i tor, sort data, etc. eg,
Pkzip, Anti Vi rus Software, etc.
Operating System (OS)
Introduction
An operating system consists of a set of programs, which controls, coordinates and supervises the activities
of the various components of a computer system. Its functions is to link between the computer hardware and the
user.
“An op er at ing sys tem is a soft ware, or a se ries of pro grams, which per forms var i ous types of func tions
in or der to man age and or gan ize files.”
Some of the most commonly used operating systems are MS DOS, WINDOWS, LINUX, SOLARIES, CP/M etc.
Functions of Operating System
It is responsible for managing all the resources attached to a computer system. These resources are the
processor and various input and output devices.
l Processing the commands.
l Controlling the execution of various programs.
l Managing devices (like storage and retrieval of files on the disks).
The functions involved in the management of resources are classified as follows
l Process Management
l Memory Management
l Input/Output Management
l Information Management
l User Interface
MS DOS
l The term DOS stands for Disk Operating System.
l It is the Microsoft Disk Operating System, developed by Microsoft for micro computers.
l It is the only OS, which can be loaded in the main memory of the computer, using a single disk.
l It is a single user operating system, which allows only one user to work on one CPU at one time.
l It is a powerful operating system that is easy to use, and handles errors effortlessly.
l It has a Character User Interface (CUI) ie, com mu ni ca tion be tween a com puter and the user is through
char ac ters (a, b, c, 1, 2, 3 etc).
l MS DOS provides all the commands for file handling such as creating, deleting, copying, viewing the
contents of files, etc.
l In DOS, one has to key in the commands on the prompt.
l Prompt is a place where commands are issued. It may look like
C:\>
or
C:\WINDOWS\>
l The mark (-) is the cursor which indicates that the command can be typed over here. This cursor keeps on
blinking on the screen System Files
l DOS software consists of many files, which are loaded into the main memory from the secondary storage
devices so as to load the OS in the computer.
l It involves of loading of three essential files of DOS, ie, MSIO.SYS, MSDOS.SYS and COMMAND.COM in
the main mem ory of the com puter.
l Loading these files into the main memory is called booting up (means that the computer is ready to function).
l Booting up is a step-by-step process that undergoes many steps to load the files.
l Once all the files are loaded, the DOS prompt (C:\>) is displayed on the screen, which indicates that the
operating system has created the shell around the hardware and the user interface is ready, and you can type
DOS commands and get them executed by your computer.
File Naming Convention in DOS
l In computer, information is stored in the form of files in the computer’s
secondary storage.
“A file is a collection of logically related information.”
l There is a definite way of writing the file name in DOS. It is divided into
two parts
n Primary name It may be one to eight (1–8) characters in length.
n Secondary name (extension name) It may be zero to three (0–3)
characters. Extensions are optional, as they are meant for describing
the contents of a file.
l The primary file name and file extensions are separated by a dot (.)
l The file name can have characters as 0–9, a–z, hyphen, underscore. Space characters is supported, but
should be avoided.
Features of DOS
l It is not case sensitive, ie, DIR and dir are treated as the same.
l While typing a command, if you get “Bad command or file name” comment, it indicates that DOS did not find
any file name matching your request. So, correct your command and enter it again.
l The file names are restricted to 8 characters only.
l It does not support space entries in the file name.
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