What is operating system ?

An operating system is an integrated set of programs that controls the resources such as CPU, memory, I/O devices etc., of a computer systemand provides its users with an interface or virtual machine that is more convenient to use that the bare machine.

An operating system is master control program that runs the computer and acts as a scheduler. It controls the flow of signals from CPU to various parts of the computer. It is first program loaded into the memory when the computer is tured on. Popular operating systems are MS-DOS, Windows and UNIX.

An operating system (also called as OS) supervises and provides services to computer users. It permits the computer to supervise its own operations by automatically calling in the applications programs and managing the data needed to produce the output desired by users. It isolates the hardware from the user. The functions provided by OS are transparent or invisible to the users.

Multimedia and Animation

Computers can be used to integrate two or more types of media, such as text, graphics, image, audio, and video, for the purpose of generation, storage, representation, manipulation ans access of multimedia information. Multimedia is one of the most commonly used terms in entertainment industry, which produces various entertainment products such as movies and video games.

Computer animation deals with the generation, sequencing, and display of a set of images to create an effect of visual change or motion, similar to a movie film (video). Animation is an important component of multimedia, because just as a picture is a powerful way to illustrate information, a small animation clip is even more powerful and useful for illustrating concepts, which involve movement.
For example, in the multimedia application meant for educating small children, an animation clip will be very effective in illustrating the difference in the movment of a horse during a gallop versus a walk. Several movies and advertisements now contain many visual tricks, which could never be accomplished without the aid of computers. For example, if you carefully watch the advertisements for detergent soaps/powders, toothpastes, insecticides for mosquitoes and cockroaches, etc., you will notice avenge in them, which cannot be videographed. These scenes are produced by using computer animation.

Ethics in Computing

Ethical conduct goes beyond merely adhering to laws. All professions have a code of ethics that broadly sets standards for professionals. Such ethical standards may not be covered by specific legislation. For example, what should you do if you are analyst or programmer responsible for a program that invades privacy ? Or how responsible are you if you create a software package that produces erroneous results ? After all, is it reasonable to expect software packages to be totally free of errors?

Of course, there are no simple answers to questions such as these. Many people with high ethical standards have argued against holding computer professionals totally responsible for their work, because the way a system is used may not be under the programmer's or analyst's control. Some people argue that, just as Alfred Nobel cannot be hold accountable for the immoral use of his invention of dynamite, computer professionals should not be hold accountable for programs that are used illegally or unethically.

As the debate over these ethical issues goes on, many leaders in the computing field believe that code of ethics is of primary importance and that it would be far better for professionals to police themselves before the government finds it necessary to pass laws.

Remote sensing and GIS

Remote sensing is the science of deriving information about the earth's land water areas form images acquired by using sensing devices operated from a remote location. It relies upon measurement of electromagnetic energy reflected or emitted from the features of interest.

The field of GIS and remote sensing has been referred to as the technology of today. The largest primary source of digital data for use in GIS is undoubtedly that created by remote sensing technology on board of sattellites and other aircraft's. Different schools of thought have different and varied definitions for geographic information system ( GIS). Tomlin defines a GIS as a configuration of computer and hardware and software specially designed for the acquisitions, maintenance and use of cartographic data. Burrough defines a GIS as a powerful set of tools for collecting storing and retrieving at will, transforming and displaying spatial data from the real world.

Thus, a GIS is a computer-assisted system for the acquisition, storage, analysis and display of geographically are spatially reference data.

Computer Gaming

Computers are also being used for playing video games. With the advent of multimedia, there has been a boom in the different type of video games available on computer systems. Sound and animation have been particularly important in these applications to make the games thrilling and exciting for the user. Because the sequence of events in such games depends on the action of the player, these programs are very interactive in nature.

Bio-informatics -Application of computer

Bio-informatics is the application of the computer technology to the management of biological information. Computers are used to gather, store, analyze and integrate biological and genetic information which can then be applied to gene-based drug discovery and development. The need for Bio-informatics capabilities has been precipitated by the explosion of publicly available genomic information resulting from the human genome project. The science of Bio-informatics, which is the melding of molecular biology with computer science, is essential to the use of genomic information in understanding human disease and in the identification of new molecular target for drug discovery. 

Health Care - one of the application of computer

Computers are also being used for planning and control purposes by health-care professionals. Computer equipment is used to monitor pulse rate, blood pressure and other vital signs. This leads to correct and fast diagnosis. Medical researchers are using computers as a tool in their search for cures of deadly diseases like cancer and AIDS.

E-business

E-business is about using Internet technologies to transform the way business processes are performed. Its most visible form is purchasing using PC and Internet. Every day, more companies and people gain access to the Internet, more purchases are executed electronically.

Custom-made Software

There are situations when none of the available pre-written software packages can meet the specific requirements of a user ( an organization or an individual ), either partially or fully. In such a situation, it becomes necessary to create a customized software package to satisfy the specific requirements. If the user has an in-hour software development team, the software package can be create in house. However, if such a team does not exist, the user must get it created by placing an order for it.

Database software

A database is a collection of records with fields. A database software is a set of one or more programs, which enables us to create a database, maintain it (i.e. add, delete and update its records), organize its data in disired fashion, and to selectively retrieve useful information from it.

Application Software

Application software or application packages are sets of one or more programs designed to carry out operations for a specified application. For example, every month a payroll package produces the payslips for the workers of a company.

Application software may be defined as software that provides an interface between the user and the system software to allow the user to perform specific tasks.

Some of the most commanly known application software are-

I) Word Processing software

II) Database software

III) Spreadsheet Software

IV) Graphics Software 

Utility Programs

Utility programs also called as utilities, are a set of programs, which helps users in system maintenance, and performing tasks of routine nature such as formatting of hard disks or floppy disks, taking backup of files, sorting of the records stored in a file, etc.

Communications software

In a network environment, communications software enables transfer of data and programs from one computer system to another.

Programming Language Translation

These are the system software, which transform the instructions prepared by programmers into a programming language into a form, which can be interpreted and executed by a computer system.

Operating Systems (pre-written software )

Every computer has an operating system software, which takes care of the effective and efficient utilization of the hardware and software components of the computer system.

System Software

A set of a one or more programs designed to operate, control and extend the processing capabilities of a computer system. These are general programs written to assist humans in the use of computer system and for making the operations of the computer system more effectively and efficient.

System software supports the following -
1) Running of other software.

2) Communicating with and controls peripheral devices such as printers, card readers, disk and tape etc.

3) Development of other application software.

4) Monitoring the effective use of various hardware resources such as memory, peripherals, CPU , etc.

The most common types of system are-

1) Operating systares
2) Programming Language Translator 3) Communications Software
4) Utility Programs

Voice Reproduction system

A voice reproduction system produces audio output by selecting an appropriate audio output from a set of pre-recorded audio responses. The set of pre-recorded responses include words, phrases or sentences spoken by human beings, music or alarms generated by musical instruments.
The application of voice reproduction system are-
I) Audio help for guiding how to operate a system. For example, bank uses voice reproduction system in ATM (automatic teller machines) to guide customers about transactions.
II) Automatic answering machines. For example, telephone enquiries for new telephone numbers in place of an old number, or vacancy status of a particular flight or train is taken care by an automatic answering machines.

Difference between inkjet and Dot Matrix Printer

Dot Matrix Printer and Inkjet Printer-
1) Inkjet printer is a non-impact printer while dot matrix printer is a impact printes.

2) Inkjet printer provide better printing quality than dot matrix printer.

3) Inkjet printers are less noisy than dot matrix printer.

4) Inkjet printer is expensive than dot matrix printer.

5) Inkjet printer resolution id good about 100 dots/cm while dot matrix printer has average resolution. 

Difference between Chain Printer and Drum Printer

Drum Printer and chain printer -
1)Chain printer uses a chain mechanism. There is one print hammer for each print position on the line. The characters are printed when the hammer presses the paper against the ribbon while in drum printer a metallic cylinder having column on the drum contains all the characters. Ad the drum rotates, each character that is to print reaches the appropriate position and a hammer then strikes that character.

2) Drum Printers are costly than chain printers.
3) In chain printers, chains may be changed easily while in drum Printers drums cannot be changed often.

Difference between Line printer and Character Printer

Character printer and line printer -
1) Line printers prints a line at a time while character printers prints a character at a time.

2) Line printer is faster than character printer.

3) Line printers are expensive than character printers.

4) Line printers are disigned for heavy printing applications and can print continuously for a few hours while character printers cannot be used continuously for more than one hour.

5) Line printers are called "heavy  duty" Printers while character printer are called "light duty " printers.

Speech Synthesizer

A speech synthesizer converts text information into spoken sentences. To produce speech , these devices combine basic sound unit called phonemes. From a given text information, sequence of words are combined into phonemes,  amplified and output through The speaker atteached to the system. Speech synthesizer are still in their infancy because they can produce only limited unique sounds with only limited vocal inflection and phrasing.

The application of speed synthesizer are -
1) For reading our text information to blind persons.

2) For allowing those persons, who cannot speak to communicate effectively.

3) For translation systems, which convert an entered text into spoken words in a selected language.

Voice Response Systems

A voice Response System has an audio-response device, which produces audio output. The output is temporary, soft copy output.
These are of two types-
(i) Voice Reproduction system

(i) Speech synthesizer

Screen Image Project

Screen Image Project is used for project information from a computer on to a large screen such as a cloth screen or a wall, so that it can be simultaneously viewed by a large group of people. A screen Image projector can be directly plugged to a computer system, and the presenter can make a presentation of a group of people by projecting the presentation material one after another on a large screen with the help of computer's mouse or keyboard. The presenter can also directly point to, mark, or edit certain portion of the content of the displayed material during the presentation to make the presentation more understandable.

Visual Display Unit (MONITOR)

Monitors are used as producing soft copy output. They display the generated output on a television like screen. A monitor is usually associated with a keyboard, and together they form a video display terminal (VDT ). A VDT ( also called terminal ) is input/output device. The keyboard is used for input to the computer and monitor is used to display the output from the computer.

The two basic types of monitors are cathode ray tube (CRT) and flat panel. The CRT monitors look like a television, and are used with non-portable computer systems. On the other hand, the flat monitors are thinner and lighter, and are used with portable computer system like notebook computer.

Advantages and disadvantages of laser printer compared to inkjet printer

Advantages-
I) It uses laser beam rather than squirting ink for printing which is a fast scheme.
II) The image quality is better than inkjet. 
III) It requires low maintenance as compared to others.


Disadvantages-
I) Generate high cost colour outputs.
II) It is costlier than inkjet printer.

Voice Recognition System or Voice Input Devices

Voice Recognition System or voice input Devices convert spoken words into electrical signals by comparing electrical patterns produced by the speaker's voice with a set of prerecorded patterns. It a machining is found, the computer accepts it as a part of its standard "Vocabulary".

Touch screen

A touch screen registers input , when a finger or other object cones in beam and ultrasonic acoustic wages. Infra-red beams crisscross the surface of the screen and when a light beam is broken, that location is recorded.

Magnetic Ink character reader (MICR)

MICR is widely used by banks to process large volumes of cheques and deposit forms, written everyday. A special ink called magnetic ink is used to write characters on the cheques and forms which are to be processed by a MICR. MICR is capable of reading characters on a paper written with magnetic ink. The magnetic ink is megnatized during the input process. The MICR reads the magnetic patterns of the written characters. To identify the character these patterns are compared with special pattern stored in the memory. Before cheque are issues to customers the identification number of the bank and the depositors account number are printed on the lower left-side of the cheques with the magnetic ink. The amount is printed on the lower right side of the cheque by the bank employee with the magnetic ink after the cheque is revived from the customer. When a cheque is entered into an MICR, it passes through a magnetic field. The iron oxide particles are magnetized under the magnetic field. The reader head reads the character written on the cheque with the magnetic ink. It interprets the characters and sends the corresponding data directly to the computer for processing.

Optical bar code readers

This method uses a number of bars or line of varying thickness and spacing between them, to indicate the desired information. Barcodes are used on most grocery items, cosmetics, paperback novels, etc. An optical bar reader can read such bars and convert them into electrical pulses to be processed by a computer. The most commonly used barcode is universal product code (UPC ). The UPC code uses a series of vertical bars of varying widths. These bars are detected as ten digits. The first five digits identifies the supplier or manufacturer of the item. The second five digits identifies individual product number. The code also contain a check digit, to ensure that the information read is correct or not.

Optical Mark reader ( OCR)

An optical mark Reader special marks such as squares or bubbles are prepared on examination answer sheets or questionnaires. The user fill in these squares or bubbles with soft pencil or ink to indicate their choice. These marks are detected by an optical mark Reader.
The OMR device has a high-intensity light that is directed as a beam at the sheet of paper being fed through it. The beam scans the sheet and detects number and location of the pencil markes. The data is then converted into electric signal for the computer.

Optical Character Reader ( OCR )

An optical character readers detects alphnumeric characters, printed or typewritten on paper. It may be a hand held scanner or a page scanner to detect light reflected from a line or from a page of the text. The change in the reflected light is converted too binary data which is sent to the processor.

Optical Scanners

The Optical Scanners are capable of reading information recorded on paper, employing light source and light sensors. The information to be typewritten information , hanf-written information, information coded as magnetic ink or pencil markes, or information coded as bars.
The following are the commonly used optical Scanners-
1) Optical Character Reader ( OCR )

2) Optical Mark Reader (OMR )

3) Optical Bar Code Readers

4) Magnetic Ink character reader (MICR )

Scanners

Scanners are a kind of input devices. They are capable of entering information directly into the computer. Important types of scanners are optical scanners and magnetic ink character readers.

Trackballs

Trackball is also a pointing device and contains a ball which can rotate in any direction. The user spins the ball in different directions to move the cursor on the CRT screen. The associated electronic circuitry detects the direction and the spin. The information is sent to the processor.

Joystick

A joystick is a positioning device. It is used to move the cursor position on a CRT screen. Its function is similar to that of a mouse. A joystick is a stick which has spherical ball at its lower end as well as at its upper end.

The lower spherical ball moves in a socket. The joystick can be moved right to left, forward or backward. The electronic circuitry inside the joystick detects and measures the displacement of the joystick from its cental position. The information is sent to the processor.

Mouse

A mouse is a pointing. As well as positioning device. It contain two or three buttons. As the rolls it on a flat surface, the mouse controls cursor movment on the screen. When the user presses one of the buttons , the mouse either markes a place on the screen or makes selections from data on the screen. It can be used for many applications, ranging from games to designing products with graphics.
It can be used as an alternative to keyboard or it can be used in combination with a keyboard to enhance input operations.

Light Pen

A light pen is a pointing device. It is used to select a displayed menu option on the CRT. It is a photosensitive pen like device. It is capable of sensing a position on the CRT screen surface, its photocell sensing element detection the light coming from the screen and the corresponding signals are sent to the processor. The menu is a set of programmed choice offered to the user.
A light pen can also be used for graphics work. A user can draw directly on the CRT screen with the light pens.

Punched Card and Card Readers

Punch card is a rigid piece of paper containing rows and column of numbers. It is put into a keypunch machine which place holes in to represent the data. This pattern of representing data as punched holes is known as Hollerith code. A card reader interpretes these holes to translate the punched information into a machine readable code and then send to the CPU for processing.
Punched cards are rarely used today. However, you may occasionally encounter in large companies such as public utilities, where they are still used for billing.

Keyboard

Programs and data are entered into a computer through a keyboard which is attached to a microcomputer or the terminal of a mini or large computer. It contains alphabets, digits, special character and some control keys. When a key is pressed, an electronic signal is produced which is detected by an electronic circuit called keyboard encorder. A keyboard encorder may be a special IC or a single-chip microcomputer. The function of an encorder is to detect which key has been pressed and send a binary code to the computer. The binary code may be an ASCII , EBCDIC , or HEX code .

A typical computer keyboard contains all the letters, number , symbols of a regular typewriter , plus other keys which may include numeric keys, special keys like control movement.

Ink-jet Printers

These are non-impact character printers, based on a relatively new technology. Ink-jet printers produce high quality output because the characters are formed by dozens of tiny ink dots. The document printer may contain multiple character styles and a variety of type sizes. Some models also allow for different colours of ink for multiple colour printing.

Dot-matrix Printers

These printers print each character as a pattern of dots. The print head comprises a matrix of tiny needles, typically seven rows with nine needles in each ( 9 x 7 matrix), which hammer out character in the form of patterns of tiny dots. The shape of each character, i.e. The dot pattern, is obtained from information held electronically in the printer.
The print quality of a dot matrix printer is inferior to that of a daisy wheel printer. But dot-matrix printer are faster than letter -quality printers in the range of 40 to 250 characters per second.

Letter-quality Printers

These printers use a print wheel font known as a daisy wheel. Each petal of the daisy wheel has a character embossed on it. A motor spins the wheel at a rapid rate.
A print hammer strikes it to produce the output. Daisy wheel printers are impact printers. Their output resembles a typed output and they are noted for their print quality. The speed of these letter-quality printers normally range from 10to 50 characters per second.

Page Printers

These are very high speed non impact printers, which can produced documents at speed of over 20,000 lines per minute. Electronics, xerography, lasers, and other technologies have made these high-volume systems possible. These techniques, called electro-photographic techniques, have developed from the paper copier technology.

Band Printers

Band printers are just like chain printers. They contain fast rotating scalloped steel print band, in place of a chain. Hammers strike the ribbon and the paper against the character to be print. Some printers can print upto 3000 lines/min.

Chain Printers

Chain printers use a rapidly rotating chain which is called is character font. The printers receive all the characters to be printed in one line from the processor. A chain may contain more than one character set. When the desired character comes in the print position, the hammer strikes the ribbon and the paper against the character. Its speed lies in the range of 400-2400 lines per minute.

Drum Printers

A drum printer consists of a solid, cylindrical drum that has raised characters in bands on its surface. There are as many bands as there are printing positions. Each band contain all the possible characters. The drum rotates at a rapid speed. For each possible print position, that is, opposite to each band of the drum, there is a print hammer located behind the paper. These hammer strike the paper, along with the inked ribbon.
Typical speeds of drum printers are in range of 300 to 2000 lines per minute. 

Laser printer

Laser printers works in the same manner as copy machines. A laser beam creates electrical charges that attract toner to from an image and transfer it to paper. Laser printers come in a variety of sizes, generally the large and faster the priter, the more expensive it is. Large laser printers used on mainframes and minicomputers where high-quality graphic output is required. Small, "personal" laser printers are suitable for home use. The laptop needs to have a built-in infrared transmitter installed, but no cable or no wires are required. Hewlett-Packard recently brought out of a wireless printer.

Characteristics of Computer and its Limitations.

The characteristics of computer are as follows-
(i) Speed - computer is a very fast device. It can perform in a few seconds the amount of work that a human being can do in an entire year. A computer can add and subtract numbers, compare letters to determine alphabetic sequence, move and copy numbers and letters. The speed varies from a few microseconds to nanoseconds.
(ii) Accuracy - Computer are very accurate. They can perform their hundreds of thousands of operation with great accuracy as their circuits have no machanical parts to wear and malfunction.
(iii) Reliability- Computer output is generally very reliable, subject to the condition that the input data entering the computer should be correct and the program of intructions should be reliable and correct. Incorrect input data and unreliable programs give us computer error and wrong results.
(iv) Storage capacity - Various computer media can store millions of character of data in a condensed form.
(v) Intangible benefits - There are many companies that utilize computers for intangible benefits such as flexibility, ability to accomodate growth and the psychological factor that may give  them a competitive edge in attracting consumers to buy their products or services.
(vi) Reduction cost - The cost of computer equipment has dropped drastically over the years.
(vii) Diligence - A computer is free from monotony, tiredness, lack of concentration, etc. And hence can work for hours together without creating any error and without grumbling.
(viii) Versatility - Versatility is one of the most wonderful feature about the computer. It is preparing the result of particular examination, the next moment it is busy for preparing electricity bills.
Computer Limitations - The computer is one of the most powerful tools ever developed. The man who was treated for pneumonia and then charged by the hospital's computer for the use of the delivery room and nursery. Such " computer failures" may be amusing. But most such foul-ups happed because people fail to consider some basic computer limitations. Without reliable programs and sounds logic, no computer system will perform adequately. 

What is a computer ?

A computer may be defined as ab electronic machine that can solve problem by accepting data, performing certain operations and presenting the result of those operations under the direction of detailed step-by-step instructions. Such a set of sequenced instructions, which cause a computer to perform particular operations, is called a program. 

Explain liquid drop model of atomic nucleus.

Explain liquid drop model of atomic nucleus.
Explanation-
According to this model a necleus can be assumed to be like a liquid drop for the following reasons-
(i) The stable necleus is spherical in shape due to symmetrical surface tension forces.
(ii) Such as the surface tension forces act on thevsurface of the liquid-drop similarly a potential barrier to surface of the nucleus acts.
(iii) The nuclear force are short range forces. Similarly, in liquid drop, the intermolecular forces are short range forces.
(iv) The density of liquid drop is independent of its volume. Similarly the density of nucleus is independent of its volume.
(v) On rising the temprature of liquid the molecules evaporate. Similarly, when energy is given to the neucleus a compound nucleus is formed which emits nucleons almost immediately . 

History of superconductivity

Superconductivity is a state exhibited by many conductors when cooled below their superconductivity transition temperature. Superconductivity is one of the most fascinating physical phenomena having a vast potentiality in practical application. A superconductor material exhibits zero electrical resistivity and complete diamagnetism. The superconducting state is influenced by temperature, magnetic field, and current. There exist critical values for these three parameters, above which values the material passes into normal state.   

What is a LASER ?

The word LASER is the short of light amplification by stimulated emission of radiation. Laser is that device is which an intense, monochromatic, coherent and uni-directional light beam is obtained. It was discovered in 1950, by Townes and Shallow.
Thus, a Laser produces a light beam in which all the waves are of same frequency.  all waves are in same phase and all waves travel in a definite direction

What is Newton's Rings

When a Plano-convex lens with its convex surface is placed on a plane glass plate, an air film gradually increasing thickness is formed between the two. The thickness of the film at the point of contact is zero. If monochromatic light is allowed to fall normally, and the film is viewed in reflected light , alternate dark and bright concentric rings with their center dark is formed between the lens and glass plate are seen. Since the phenomenon was described by Newton that is way the rings are known as Newton's Rings after his name.

Explain the Interference of Light.

When two light waves superimpose, then the resultant amplitude ( or intensity ) in the region of superposition is different then the amplitude of individual waves. this modification in distribution of intensity in the region of superposition is called inerteference. 
When the resultant amplitude is the sum of the amplitudes due to two waves, the interference is known as constructive interference and when the resultant amplitude is equal to the difference of two amplitude, the interference is known as destructive interference.


Types of interference-
i) Division of Wavefront
ii)Division of Amplitude

What is core type transformer ?

Constructionally there are rwo types of transformers i.e. Core type transformer and Shell type transformer. There are differ from each other by the manner in which the winding are wound around the magnetic core.
Core type transformer- in Core type transformers , the windings surround a considerable part of the core, i.e. The half turns of primary and secondary windings are placed on each limb (core).
Generally, circular coils are used in core transformer because of their mechanical strengh. Such cylindrical coil are wound in helical layer with the different layers insulated from each other by paper, cloth, micarta board or cooling ducts. Figure shows the diagram of Core type transformer.

What is Compton Effect?

In 1921, Professor A.H. Compton discovered that whrn a mono-chrometic beam of light of high frequency radiation ( X-rays, Y-rays, etc.) is scattered by a substance, the scattered radiation contain two components
-One having a lower frequency or greater wavelength and the another having the same frequency or wavelength.
The radiation of of unchanged frequency in the scattered beam is knows as unmodified radiation while the radiation of lower frequency is called as modified radiation.
And the difference in wavelength is known as Compton Effect.