Which is used to communicate our feelings with others called language. In computers language used to make programs. In computer there are three types of languages.

a). High Level Language : In this language the instructions like humanlanguages. That means english like language.


1. BASIC (Beginners All Purpose Symbolic Instruction Code)

2. COBOL (Common Business Oriented Language)

3. PASCAL (It's a name of the scientist who invented the first

mechanical adding machine)

4. FORTRAN (Formula Translation)

b).Low Level Language : In this language all the instructions in machine code.

Ex: 8086,8088

c).Middle Level Language : These languages are made up using the high level and low level language features.

Ex: C language, ADA language



Collection of programs or bunch of programs called as software. Softwares are of two types:


This is that software, which serves specific purposes and allow the user to create applications which are for a given purpose like financial accounting, payroll, examinations, human resources management etc. These software can be further classified, depending upon the source of development as well the users.


These are those software packages, which are developed by group of people or an individual to used by others. The most commonly available pre-

written application software are:

a). Word Processing Software: These are those software, which usually automate the day to day documentation work of an organization. t helps in creating texts, manipulating, formatting and printing of the text, so that the drafting, redrafting, typing again and again manually now becomes easy and less paper wastage as well the time taken also is reduced a lot. Wordstar, wordperfect, microsoft word etc. are some of the available wordprocessors.

b). Electronic Spread Sheets: Electronic spread sheets are like sheets of paper with rows and columns. ESS allow numbers, characters, formulae and all other types of data which has to be entered in tabular form into rows or columns. Usage of ESS gives significant advantages and benefits over using paper spread sheets. Some of the most commonly available and used spread sheets are lotus 1-2-3, MS-Excel, supercalc etc.

c). Data Base Management System: Data base is an organized collection of data, which is logically related. The data has to be managed so that the retrieval of information is effective and easy. Managing data involves creating, deleting, updating, adding, modifying data in databases. Along with these querying are printing reports also comes as DBM. DBMS is a software package that allows a user to perform above functions. It also allows multiple computers sharing the data files. Some of the DBMS Packages commonly used by people are Dbase, FoxPro, Clipper, Paradox etc.

This DBMS technology has been subjected to many improvements and advanced DBM software has been evolved which are called RDBMS (Relational Data Base Management Systems), ORDBMS (Object-oriented RDBMS) etc. Oracle, Ingress, Sql server, Informix, Sybase, Db2 etc. are the some examples.


This is that software which is used for developing or running a computer system. This software controls all processing activities and makes sure that the resources and the power of the computer are used in most efficient manner. Systems software consists of following softwares.

a). Operating Systems: Operating system is set of programs that control and support hardware and provide various services which are used for better operating performance of the computer. The major functions of any operating system are:

1. It assigns processors to tasks

2. It manages memory and other storage areas.

3. It act as a command interpreter.

4. File management.

5. Input - Output management.

6. Establishing data security & integrity.

7. Maintains account of processor time for billing purposes.

8. Provides data and time services etc.

The operating system can be classified as single user and multy user depending on the number of users working on it at a given point of time.

DOS is a good example of single user operating system and UNIX, Windows -NT, LINUX etc. are some of the common multy user operating system.

b). Language Processors: As a digital computer accepts digits and characters as input, however this input is not understandable;e by the computer. To make the computer understand it, the input has to be conversed into machine language. The software which makes this conversion and increases the productivity of the programmer are called language processors or translators. There are two basic types of translators.

1. Compiler: Compiler is a software that will accept the totalprogram code as input and then converts it into machine code, that means converts source code into object code.Ex: COBOL, C.

2. Interpreters: Interpreter also does the same task of compilerbut it does in a different manner. The interpreter takes the program code (source code) line by line and converts it into machine (object code).

c).Utility Tools : These utilities are those software programs are provided by the manufacturer of various hardwares to perform specific tasks commonly used to all data processing installations. Device drivers, directory and file management utilities are the some examples.



All the physical components which are placed in a system called as Hardware.

Ex: Mouse, CPU, Keyboard etc.

PROGRAM: To accomplish a task we are giving several instructions to the computer. These instructions used to tell the computer what to do, how to do and when to do. These set of instructions called as program.



Computers in general can be classified into two major categories based upon the following criteria.

a). According to the logic used by the computer

b). According to the size of the computer.


Computers can classify into three categories based upon logic used. They are:

a). ANALOG COMPUTERS: These are the computers, which operate on the principle of creating a physical analog of mathematical problems. These computers continuously measure physical variables. These computers used signals as input, which can come from devices like thermometers, speedometers, barometers etc. These signals are continuous flow of physical quantities.

Ex: Temperature, speed, pressure etc.

Which vary continuously. The result given by these computers usually is not very precise, accurate and consistent.

b). DIGITAL COMPUTERS: These are the computers which accepts digits and alphabets as input, which are used for solving, controlling any problem which can be expressed mathematically. These computers take data inform of zero's and one's.

c). HYBRID COMPUTERS: As any hybrid is combination of best qualities of the available types, so that it becomes the best by adopting best qualities of given variety of objects. The hybrid computers are those computers which adopt the best qualities of digital and analog computers. Thus becoming capable to work on analog or digital data. These computers are mostly used for automation of various complicated physical processes and machines.



Memory in a computer system is required for storage on subsequent retrieval of the instructions and data. Memory measured in bytes.

8 bits - 1 Byte

(BIT stands for Binary Digit. That means 0 and 1)

1024 Bytes - 1 KB (Kilo Byte)

1024 K Bytes - 1 MB (Mega Byte)

1024 M Bytes - 1 GB (Giga Byte)

1024 G Bytes - 1 TB (Tera Byte)

In computers there are two types of memories.


Primary memory consists of semiconductor memory chips and is used to store the data and programs currently in used. Each storage element of memory is directly (Randomly) accessible and can be examined and modified without effecting other cells and hence primary memory is also called RAM (Random Access Memory). Main memory stores a variety of critical information required for processing the CPU. The memory unit stores all the information in memory cells also called memory locations in binary digits. Each memory location has a UNIQUE address. The RAM is a volatile memory.


Secondary memory is used to store the information permanently. It is non-volatile memory. This is also called auxiliary or permanent memory. The devices which are used for permanent memory are called as secondary storage medias. Which is external to a computer. The following are some of the commonly available categories of secondary

storage devices.

MAGNETIC TAPES: There are used as external storage devices apart from being used as high speed input and output devices. These devices use a tape which is about 12.5mm to 25mm wide and about 500 meters to 1200 meters long. This tape is usually made of a plastic known as mylar. This tape is quite similar to the audio cassette tape. The tape is coated with very thin layer of iron oxide, a magnetic material.

MAGNETIC DISKS: Magnetic disks are very popular means of secondary storage. A magnetic disk is usually made up of plastic like material called mylar coated with ferromagnetic materials. These disks come in various sizes. These magnetic disks can be divided into two major categories. They are:

a). floppy disks (b). fixed or hard disks

All these disk surfaces are composed on concentric circles called tracks. Data is stored on these tracks. The tracks are further divided into sectors.

OPTICAL DISKS: Optical disks are alternate mass storage devices with huge capacity. In optical storage devices the information is written using laser beam. These devices which are memories can store large amount of data.Ex: CD (Compact Disc), DVD (Digital Versatile Disc)


A floppy disk is small, flexible, faster and cheap alternative to storage using magnetic film. This was developed in early 1970's, is one of the popular media for data storage. This disk is made up of flexible plastic material, coated with magnetic materials like ferrous oxide. The floppy disk is packed in protective paper or plastic envelope. All the disks have two sides. Floppy diskette comes in two

basic sizes at present as follows:

a). 5 1/4 inch floppy disk (mini floppy)

b). 3 1/2 inch floppy disk (micro floppy)

The floppy's surface has to be divided into tracks and sectors.

a). MINI FLOPPY: These floppy's are again divided into two tydependends upon their storage capacity.

1. DSDD (Double Sided Double Density)

2. DSHD (Double Sided High Density)


The maximum capacity is 360 KB The maximum capacity is 1.2 MB

40 tracks per side (TPS) 80 tracks per side (TPS)

9 sectors per track (SPT) 15 sectors per track (SPT)

Each sector can store 512 Bytes Each sector can store 512 Bytes

b). MICRO FLOPPY: Micro floppy's are again divided into 2 types.

1. MF2DD (Micro Floppy Doublesided Double Density)

2. MF2HD (Micro Floppy Doublesided High Density)


The maximum capacity is 720 KB The maximum capacity is 1.44 MB

80 tracks per side (TPS) 80 tracks per side (TPS)

9 sectors per track (SPT) 18 sectors per track (SPT)

Each sector can store 512 Bytes Each sector can store 512 Bytes


Hard disk also called as fixed disk. These fixed disk is usually made from aluminum or other materials instead of mylar or other plastic like material. These are non-removable disks,which typically holds 10 MB to 160 GB of data. These are provide substantially fasterdata access compared to floppy disk and provide very large data storage for on-line retrieval. These disks have multiple platters, which are stacked vertically, normally at a distance of an inch. This is known as a disk pack. A disk pack can contain multiple heads mounted with the same arm. This entire pack is called as Hard Disk Drive.


The compact disc is creating revolution in the secondary storage media. In CD's the information is stored evenly across the disk in segments of the same size. As discussed earlier, the data is stored sequentially along a spiral track. In this disc random access becomes more difficult because locating a desired address involves first moving the head to the specific area then adjusting the rotation speed and then reading the address, and then to find and access the specific sector.