November 2011 ~ Computer tricks and Pranks

Printer

Printer is an output device. The most common method of producing human readable out put is using printers. Printed output is usually referred to as hard copy. Printers provide information in a permanent readable form. They produce printed output of results, programs and data. Printers are classified as follows:

1. Character printers – They prints one character of the text at a time.
2. Line printers - They prints one line of the text at a time.
3. Page printers - They prints one page of the text at a time.

Above classifications of printers are based on how they print. Besides these printers can also be classified on the basis of technology used in their manufacture. i.e.

• Impact printers-
They use electromechanical mechanism that causes hammers or pins to strike against a ribbon and paper to print the text. e.g. dot-matrix, daisy wheel.

•Non Impact printers-
They don't use electromechanical printing head to strike against ribbon and paper. But they use thermal, chemical, electrostatic, laser beam or inkjet technology for printing the text.e.g. Laser printers, inkjet printers, thermal printers.

Types of Printers:
1.Character Printers:
Character printers print one character at a time. They are low speed printers. Their printing speed is 300-600 characters per second depending upon the type of the printer. Characters to be printed are sent serially to the printer. There are two types of character printers.
a)Dot Matrix Impact Type Character Printers –
A character is printed by printing the selected number of dots from a matrix of dots. The formation of a character has been shown using 5-dot rows and 7-dot columns. This pattern is called 5x7 dot matrix. A dot matrix printer is faster than a letter quality printer. Dot matrix printers are very flexible. They don't have fixed character font. The term font is used to refer to a character set of printer. As the fonts are not fixed, a dot matrix printer can print any shape of a character by the software. To print graphics the dot pattern for each column of dots are sent out to the print head from the memory. Its print quality is not as good as that of a letter quality printer. It is a noisy printer.
b) Letter Quality Impact Character Printers –
A daisy wheel type letter quality printer was used in the past for good quality printing. It is no longer used .It has embossed characters just like those of a type writer. The characters are embossed on leaves placed on a wheel. An electric motor is used to rotate the wheel rapidly. When the desired character comes in the correct position a solenoid-driven hammer strikes against the ribbon to print the character on the paper.

2. Ink-Jet Printers:
These works in a similar manner to a dot-matrix printer, but instead of pressing a dry ink against the page, the print head sprays drops of liquid ink onto the page. Ink jet and bubble jet printers have better image quality and are faster than dot-matrix printers; however, printouts have a tendency to smear if gotten wet.
3. Laser Printers:
These work in a manner similar to a photocopier. A roller is charged with electricity, and then a laser is used to remove the charge from portions of the roller. Powdered ink (toner) sticks to the parts of the roller that were hit by the laser, and this toner is transferred from the roller to the paper. Then the ink is baked into the paper using a heater. Laser printers produce very high quality output and are very fast.
4. Line Printers:
A line printer prints one line of the text at a time. A non impact type line printer may use electrostatic, thermal, thermal-wax transfer or solid ink technology. Whether a non impact printers using above mentioned technology is a line printer or character printer depends on its mechanical arrangements. If several points causing impressions are in row, the printer put dots in horizontal line by scanning process and print a line at a time are line printers. The impact type line printers are of the following types:
a) Drum Printer
b) Chain Printer
c) Band Printer
a) Drum Printer:
A line printer in which the type is mounted on a rotating drum that contains a full character set for each printing position is called Drum Printer. Each character position along the text line contains a band of raised character set. There is a magnetically driven hammer in each character position of the line. The printers receive all characters to be printed in one line of the text from the processor. The hammer hit the paper and ribbon against the desired character on the drum when it comes in the printing position. Its noise level is high and its speed varies from 200 to 2000 lines per minute.
b) Chain Printer:
An impact printer that carries the type slugs by links of a revolving chain is called chain printer. Each link of the chain is character font. Magnetically driven hammers are there in each print position. The printers receive all the characters to be printed in one line from the processor. Printers print one line at a time. When the desired character comes in the print position the hammer strikes the ribbon and paper against the character. The noise level of this printer is high and its speed lies in the range of 400-2400 lines/min.

c) Band Printer:
Band printers are just like chain printers. They contain fast rotating scalloped steel print band in place of a chain. The print bands contain raised character set. Hammers strike the ribbon and the paper against the character to print the character. Some printers can print up to 3000 lines/min.Their noise level is high.

Operating Environment

i. Operating or Target Environment:

The hardware that supports a language has a great impact on language design. Languages, as a mean to solve a problem, are part of the overall technology that is employed. The external environment supporting the execution of a program is termed its operating or target environment.

In computing, an operating environment is an environment in which users run application software, whether by a command-line interface or a graphical user interface. An operating environment is usually not a full operating system but is a form of middle ware that rests between the OS and the application.

ii. Host Environment:
The environment in which a program is designed, coded, tested and debugged is called host environment. Host Environment may be different from the operating environment in which the program ultimately used.

A quiet host environment is important because it protects enclosures used as narration environments from outside noise. It is also the work site for monitors and frequently the work site for reviewers. The task of monitoring and reviewing requires continuous, concentrated attention to acoustical details, and noise in the host environment affects how well that task can be accomplished. The host environment should be free from airborne noise and structure-borne noise.

iii. Batch Environment:
The earliest and simplest operating environment consists of external files of data. A program that takes a set of data files as input processes the data and produces a set of output data files. This operating environment is termed as batch-processing. In batch processing, the input data are collected in batches on files and are processed in batches by the program.

Languages such as FORTRAN, COBOL, and Pascal were initially designed for batch-processing environments, although they may be used now in interactive or in an embedded-system environment. The 80-column punch card which is developed by Herman Hollerith is used in the 1890 U.S census, was the ubiquitous sign of computing in the 1960's.

In a batch processing environment, an error that terminates execution of the program is acceptable but costly because often the entire run must be repeated after the error is corrected. In this environment, no external help from the user is immediately handling or correcting the error is possible. Thus, the error and exception handling facilities of the language emphasize error/exception handling with in the program so that the program may recover from most errors and continue processing without terminating.

Batch processing environment is the lack of timing constraints on a program. The language usually provides no facilities for monitoring or directly affecting the speed at which the program executes.

iv. Interactive Environment:
In an Interactive Environment, a program interacts directly with a user at a display console during its execution, by alternately sending output to the display and receiving input from the keyboard or mouse. Word processing systems, spreadsheets, video games, database management systems are examples which is used in Interactive Environment.

The characteristics of interactive I/O are sufficiently different form ordinary file operations that most languages designed for a batch processing environment experience so difficulty in adapting to an interactive environment.

Error handling in an interactive environment is given different treatment. If bad input data are entered from a keyboard, the program may display an error message and ask for a correction from the user. Language features for handling the error within the program are of lesser importance. Unlike batch processing, termination of the program in response to an error is usually not acceptable.

Interactive programs must often utilize some notion of timing constraints. An interactive program that operates so slowly that it cannot respond to an input command in a reasonable period is often considered unusable.

v. Embedded-system Environment:
A computer system that is used to control part of a larger system such as an industrial plant, an aircraft, a machine tool, an automobile, or even your toaster is termed an Embedded Computer System.

Programs written for embedded systems often operate without an underlying operating system and without the usual environment of files and I/O device. Instead, the program must interact directly with nonstandard I/O devices through special procedures that take account of the peculiarities of each device. Access to special devices is often provided through language features that give access to particular hardware registers, memory locations, interrupt handlers, or subprograms written in assembly or other low-level languages.

Error handling in embedded systems is of particular importance. Ordinarily, each program must be prepared to handle errors internally, taking appropriate actions to recover and continue.

Embedded systems almost always operate in real time. i.e. the operation of larger system within which the computer system is embedded requires that the computer system be able to respond to inputs and produce outputs within tightly constrained time intervals.

Finally, an embedded computer system is often a distributed system composed of more than one computer. The program running on such a distributed system is usually composed of set of tasks that operate concurrently, each controlling or monitoring one part of the system.

Difference between Magnetic and Optical Storage

Magnetic Storage
a) Stores data in magnetic form.

b) It is affected by magnetic field.
c) It has high storage capacity.
e) It doesn't use laser to read/write data.
f) Magnetic storage devices are ; Hard disk , Floppy disk, Magnetic tape etc.

Optical Storage
a) Stores data optically & used laser to read/write.
b) It is not affected by magnetic field.
c) It has less storage than hard disk.
e) Data accessing is high as compared to floppy.
f) Optical storage devices are; CD-ROM,CD-R,CD-RW, DVD etc.

Difference between LCD, LED, CRT

LCD
a) LCD stands for Liquid Crystal
Display which is a thin, flat display
screen made up of any number of
color or monochrome pixels
arrayed in front of a light source
or reflector.
b) It is often used in electronic
Devices because it uses very small amounts of electric power.

LED
a) LED stands for Light
Emitting Diode which is a semiconductor diode that
emits incoherent narrow-
spectrum light when
electrically biased in the
forward direction of the p-n junction. This effect is a
form of electroluminescence.
b) It can be used as a
regular household light source.

CRT
a) CRT stands for Cathode
Ray Tube which is a tube
coated with phosphorous in
inner surface. When electrons
produced by e-gun come in
contact with phosphorous
wall, light is produced by
virtue of which we can see.
b) It is generally used
in TV screens, monitors, etc

Impact of computer on society

Everyone knows that this is the age of computer and vast majority of people are using computer. Development of science and technology has direct effect on our daily life as well as in our social life. Computer technology has made communication possible from one part of the world to the other in seconds. They can see the transactions in one part of the world while staying in the other part. Computer development is one of the greatest scientific achievements of the 20 th century. Computers are used in various fields as well as in teaching and learning. Some of the major computer application fields are listed below.
1. An aid to management: The computer can also be used as a management tool to assist in solving business problems.
2. Banking: Branches are equipped with terminals giving them an online accounting facility and enabling them to information as such things as current balances, deposits, overdrafts and interest charges.
3. Industrial Application: In industry, production may be planned, coordinated and controlled with the aid of a computer.
4. Engineering Design: Computer help in calculating that all the parts of a proposed design are satisfactory and also assist in the designing.
5. Meteorology: Data is recorded at different levels of atmosphere at different places, using remote sensors carried on a satellite.
6. Air Travel: Small computers are installed as a part of the plane's equipment.
7. Road Traffic Control: Computers assist with the control of traffic lights.
8. Telephones: Computerized telephone exchanges handle an ever increasing volume of calls very efficiently.
9. Medicine: Computers are widely used in hospitals for such task as maintaining drugs, surgical equipments and linen, for payroll and also for checkup and treatment of diseases.
In addition computers are also used for recording and film studios, research, military, etc.
Computers have both positive and negative impact in our daily life as well as in our social life. But the gross development of the nation is faster with the application of computers in industries and education. The both positive and negative impacts of computers are listed below.
Positive Impact of Computer -
• The work can be done in very less time.
• More information can be stored in small space.
• Multitasking and multiprocessing capabilities of data.
• Easy to access data.
• Impartiality.
• Documents can be kept secret.
• Error free result.
• It can be used for various purposes. i.e. It can be used in any type of work.
Negative Impact of Computer -
• Highly expensive.
• Accidents.
• Data piracy.
• Increased Unemployment.
• Huge data and information can be lost sometimes.
• Fast changing computer technology.
• Service distribution.
• Illiteracy of computing and computers.

As mentioned on the above list, computers have both positive and negative impact in our society. But the use of computer is increasing day-by-day.

History of Computer in Nepal

There is not a long history of computers in Nepal. Nepal hired some types of calculators and computers for it's census calculation. Following list shows it's history in Nepal.• In 2018 BS an electronic calculator called "Facit" was used for census.• In 2028 BS census IBM 1401 a second generation mainframe computer was used.• In 2031 BS a center for Electronic Data Processing ,Later renamed to National Computer Center(NCC),was established for national data processing and computer training.• In 2038 BS ICL 2950/10 a second generation mainframe computer was used for census.• Now-a-days probably each and every institutions, business organizations, communication centers, ticket counters etc are using computers.