Q Explain input and output device of computer.
The keyboard is one of the earliest and the most commonly used input device for entering data and commands into the computer system. The traditional QWERTY typewriter comprises the basic
portion of today’s computer keyboards. It is a collection of different switches or keys.
Keyboard are divide in Five Groups.
1) Alphanumeric keys :- A to Z, 0 to 9 and Special Symbol
2) Numeric Key :- 0 to 9, +, -, /, *, Enter, ., num lock
3) Cursor movement key :-
4) Function key :- F1 to F12
5) Special purpose key :- Alt, Ctrl, Tab, ESC, Scroll Lock, Pause, break, Print screen,. Insert, delete, end, home, page up, down.
b. Process of accepting input from the keyboard
i) When a key is pressed, a computer circuit called keyboard controller puts a code (scan code of the key) into a memory called keyboard buffer.
ii) The keyboard controller signals the computer's system software that a key has been pressed by sending an interrupt request.
iii) The system software then reads the keyboard buffer and sends the key's scan code to the CPU.
A mouse is a pointing type of input device. It usually contains one or three buttons; as the user rolls it on a flat surface, the mouse controls cursor movement on the screen. When the user presses one of the buttons, the mouse either marks a place on the screen or makes selections from data on the screen. It can used for many applications ranging from games to designing products with graphics. It can be used as an alternative to keyboard.
The operations can be performed using a mouse in two steps:
ii) Clicking, Double-clicking, Dragging or Right-clicking the buttons, which are on the mouse. These points are explained below:
Clicking: Pointing to an item and quickly pressing and releasing the mouse button is called as clicking.
Dragging: Holding down the mouse button while over an object will grab on to it. If you move the mouse while holding down the mouse button you will be able to move (drag) the object to a new place on the screen.
Dropping: After dragging an item, releasing the mouse button will leave (drop) the object at the new place on the .
a. The Mouse moves the cursor around the screen faster than using keystrokes.
a. Requires moving hand from keyboard to mouse and back.
b. Repeated motion can lead to carpal tunnel syndrome.
This is a ball inserted in a small external box adjacent to and in the same unit as the keyboard of some notebook computers (laptops). The ball can be rotated by hand in nay direction.
i. Does not need as much desk space as a mouse.
ii. Is not as tiring since less motion is needed.
i. Requires fine control of the ball with just one finger or thumb.
ii. A repeated motion of the same muscles is tiring and can cause carpal tunnel
5) Light Pen
A light pen is also a pointer device like mouse. It can be used with hand-held computers and digital assistants. This pen-like device (also called stylus) is held in the hand and is used to write on a special pad or directly on the screen. It can also be used like a mouse for selecting commands. Light pen is useful for graphics work.
Pen based computers are not generally used to enter large amount of text but for selection of a menu or icon, inputting signatures or messages.
6) Touch Screen
Touch screens accept input by allowing the user to place a fingertip directly on the computer screen, usually to make a selection from a menu.
They use sensors in or near the computer's screen to detect the touch of a. finger. When the sensor detects the touch of a finger, it sends the information to the CPU
A joystick is most popular input device used to play video Games. A Joystick uses a level to control the position and speed with which the joystick is moved into digital signals that are sent to the computer to control the cursor. A joystick is similar to a mouse except that with a mouse the cursor stops moving as soon as you stop moving the mouse. Joysticks are mostly used for computer games, but they are also used occasionally for CAD/CAM system and other applications.
1) Magnetic Ink Character Reader (MICR)
In this method, human readable characters are printed on documents using special magnetic ink. A magnetic ink character reader can recognize these characters. The MICR devices use the E13B font, which contains digits 0-9 and 4 special symbols as shown in fig.
MICR is especially used in banking. A bank cheque contains branch code cheque number and account number preprinted in magnetic ink(iron oxide particles). The MICR reader can read data directly from the cheque into the computer system. This eliminates manual data entry and ensures accurate data entry.
2) Optical Bar Code Reader (OBCR}
Bar Coding is a method of printing bars varying thickness and spacing. They are printed on items like books, package etc. The bar codes provide information like manufacturer, product code, price etc. A sample bar code is as follows.
3) Optical Character Reader (OCR)
An optical scanner is a device, which reads an image and converts it into a set of 0s and 1s which can be stored in computer memory. The image may be handwritten, typed or printed document.
In order to speed up the process, American National Standards Institute (ANSI) adopted a standard style of text to be used with Optical Character Reading Devices which converts the characters into a set of 1s and 0s. This is called the 'Bitmap'.
These scanners can be either hand held or flat bed scanners. These scanners emit light pulses. Black areas of the text do not reflect the light and white areas do.
The reflected light is sensed by photo-diodes, which generate electronic pulses corresponding to the light intensity.
A monitor is a television like device used to display input data or information allowing users to view the results of processing. Quality of the monitor is often judged in terms of resolution which is a measure of the number of picture elements, or pixels, a screen contains. A pixel is the smallest increments of a display screen that can be controlled individually. The high number of pixels, the clearer and sharper is the image. Screens for monitor are of two types.
a) CRT ( Cathode Ray Tube)
b) LCD( Flat-Panel Monitor)
a) CRT Monitors
These monitors have a Cathode Ray Tube (CRT). This tube contains an electron gun at the back, which generates an electron beam, which is guided by magnetic coils to the front of the CRT where there is a screen.
The guiding assembly consists of a control grid (to regulate beam intensity), focus grid (to control beam width), an accelerating grid, horizontal and vertical deflection coils to move the beam across the screen.
The back of the screen is coated with phosphor, which glows when the electron beam strikes it. A shadow mask is placed very close to the phosphor coating. It is a metal plate with holes. This mask blocks the beam detracting from the brightness of the resulting image.
A color monitor also works in the same way but has three electron guns (Red, Green, and Blue).
The smallest phosphor dot which can be illuminated is called a 'pixel'. Each character is displayed by a matrix of 5 dots along horizontal and 7 dots in vertical direction. A display normally has 80 characters in a horizontal line and 24 such lines vertically.
b) Liquid Crystal Display (LCD)
The Liquid Crystal Display is most commonly used in calculators and is now being : used for monitors too. The LCD consists of a special polymer called Liquid Crystal. The Liquid Crystal is sandwiched between two transparent electrodes or conductors using which an electric field can be applied.
A printer is a peripheral output device designed to get a hard copy of the output.
Printers are of two types:
i) Impact Printer
ii) Non Impact Printers
1) Impact Printer
Impact printers create an image by pressing an ink ribbon against the paper using pins or hammers.
Example: Dot matrix printer
1) Dot Matrix Printers (sum 03,): It is an impact printer most commonly used in offices etc. where physical impact with the paper is important, such as when the document has carbon-copies.
It uses a print heads contain 9 pins or 24 pins. Theses pins produce patterns of dots on the paper to form the individual characters.
These printers have a speed of about 30 cps to 600 cps (characters per second). However, being impact printers they are noisy and print quality is not very good. Since they cost less, they are widely used for daily and bulky printing jobs.
2) Non-Impact Printer
Non-impact printers are much quieter than impact printers as their printing heads do not strike the paper. Most non-impact printers produce dot-matrix patterns. Several different technologies have been used to provide a variety of printers.
Example: Inkjet, Laser, Thermal printers
Depending on their speed and approach of printing, printers are also classified as character printers, line printers, page printers.
1. Laser Printers
These printers are more expensive than inkjet printers, faster and give better print quality. These printers have a LASER which is controlled by a processor within the printer. It is a page printer as it scans the entire page to print.
The laser when aimed at the electro statically charged drum by the spinning multi-sided mirror creates an electrical charge. Toner which consists of tiny particles of oppositely charged ink, sticks to the drum on the places that are charged.
Then, the toner is transferred to the paper by pressure and heat. The drum is continuously rotated so as to form the full image.
a. They have a resolution from 600 dpi to 1200 dpi.
b. They can print 4-16 pages per minute.
c. They are very expensive.
2. Inkjet Printers
These are non impact character printers based on a new technology. They print characters by spraying small drops of ink on the paper.
Its print head has up to 64 tiny nozzles that are selectively heated up within microseconds. Due to heat the ink vaporizes and is ejected through the nozzle.
The droplets are electrically charged after leaving the nozzle which is then guided to the proper position on the paper by electrically charged deflection plates.
Inkjet printers produce high quality output because the characters are formed by dozens of tiny ink dots. Inkjet printers are the high speed printers.
The print head is attached to an ink cartridge(s) such as separate black and color cartridge or both in a single cartridge.
The cartridges of some Inkjet printers include the print head itself. The cartridge has an ink reservoir, which has one or more nozzles. Color inkjet printers have four nozzles (cyan, red, yellow and black).
A stepper motor moves the print head assembly (print head and ink cartridge back and forth across the paper. A roller-feed mechanism moves the paper up one line at a time.
a. Inkjet printers generate higher quality output than dot-matrix printers.
b. They are extensively used for printing graphics.
c. The resolution is about 360 dpi(dots per inch).
d. Speed is about 2 to 4 ppm.
e. Initial cost is less but operational cost is high as compared to dot matrix printers.
3. Thermal printers
Thermal printers use two types of printing technologies: direct thermal and thermal transfer printing. The coating on the thermal paper turns black in the areas where it is heated, producing characters or images. Direct thermal printers have no ink, toner or ribbon. These printers are durable, easy to use and cost less to print than other printers. However, the thermal paper is sensitive to heat, light, water, and abrasion and the text and images may fade over time.
Thermal printers are often used in cash registers, ATM and point-of-sales terminals.
Thermal printer is not the same as thermal inkjet printer. The latter uses inkjet print technology by heating liquid ink to form vapor bubble, which forces the ink droplet onto the paper from the nozzle.
4. Daisy Wheel Printer
This printer uses 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. When a desired character spins to the correct position, a print hammer strikes it to produce the output. Thus daisy wheel printers are the impact printers. The speed range normally ranges from 10-50 characters per second.
5. Line Printers
Line printers are impact printers used with most medium and large computers for producing high volume paper output. They are fast printers having speeds in the range of 300 to 3000 lines per minute.
A plotter is a special kind of output device used to print large-format images such as engineering drawings, maps, charts, architectural drawings etc.
They differ from printers in that they draw lines using a pen as a result of which they can produce continuous lines. Plotters are of two types
a. Table or Flatbed Plotters
b. Roller or drum plotter
Q. What is Software? Explain type of Software?
Software is the intangible part of computer. It consists of a set of instructions that tell computer what to do. A set of instructions is called a program. A set of programs is called a package. The sum of total program and packages used on the computer is called software.
Practical compute system divide software system into three major classes system software, programming software and application software, although the distinction is arbitrary and often blurred.
1) System Software: System software helps run the computer hardware and computer system. It includes operating system, device drivers, diagnostic tools, servers, windows systems, utilities and more. The purpose of system software is to insulate the applications programmer as much as possible from the details of the particular computer complex being used, especially memory and other hardware features, and such as accessory devices as communications, printers readers, readers, displays, keyboards etc.
2) Programming Software: Programming software usually provides tools to assist a programmer in writing computer programs and software using different programming language in a more convenient way. The Tools include text editors, Compilers, interpreters, linkers, debuggers, and so on. An integrated development environment (IDE) merges those tools into a software bundle and a programmer may not need to type multiple commands for compiling, interpreting, debugging, tracing and etc.
3) Application software: Allows end users to accomplish one or more specific task. Typical applications include industrial automation, business software, educational software, medical software, databases and computer games. Businesses are probably the biggest users of application software but almost every field of human activity now uses some form of application software.
Application software, on the other hand, is software that is developed for specific purpose or ‘application’ such as payroll or inventory control application software is written for a specific operating system. It interacts with the operating system which in turn interacts with the hardware to process the data.
For ex. : Let us consider a payroll system, which falls under the category of Application software.
Some ex. Of application software are :
a) Payroll processing software
b) Inventory Control
c) Accounting software
d) Word processing software
f) Graphics etc.
What is Virus? Explain type of Virus. (Win 09,
“Executed objects, initially created by a programmer, having capability to hide/ replicate in some other executable object and optionally having the capability of destruction are referred to as VIRUS”.
It is a program that attaches themselves to other programs to spread from one machine to another. It’s effect may be begin, it simply display a harmful message or change the colour on the screen. Or it may be destructive corrupting data files or even destroying the entire contents of a hard disk.
The computer virus is nothing but a program that “infects” other legitimate programs by making copies of itself. If continues to a number of other programs files, or operating system.
What is the type of computer Language ? Give Details.
Computer languages have evolved over the year from the earliest machine languages to the recent natural languages. The various stages in the language evolution is as shown :
1) Machine Languages
These languages were the earliest languages developed. Features of low level languages are :
a) These languages are greatly hardware dependent i.e. the code has to be written for specific hardware.
b) Programs written on one machine will not run on another
c) Programmers are required to have knowledge about the hardware as well.
It is one of the earliest language (1940s). All the computer use binary digits language instructions consist of strings of binary numbers. 1s and 0s indicate the on and off states of electronic circuit of computer hardware. It is also called as low level programming language. These language are machine dependent of hardware translator. It is very difficult to remember the machine language instructions because they are different combinations of 1’s and 0’s.
Since the computer circuits can directly interpret 0 and 1 execution of programs is very fast.
i) Writing programs in binary is very difficult.
ii) It is very easy to make errors during writing or data entry.
iii) Debugging is very difficult.
iv) There is no distinction between the instruction and operands or data
2) Assembly Languages
These were developed in the 1950s to remove the disadvantage of machine languages. It is one of the First Steps in improving the program preparation process. In language, Small English like words, called mnemonics were used for these languages, small English like words called mnemonics were used for instructions and hexadecimal codes were used for data.
This is also machine dependent and very from CPU to CPU. Programming using assembly language also required detailed knowledge of hardware. The only advantage is it instruction set is in English language like MOV, ADD, SUB and PUSH etc.
Therefore Assembly language mnemonics are converted into corresponding binary patterns. This conversion is done by using another program called as Assembler.
a. Writing of programs became easier
b. Errors were reduced
c. Identification and modification of errors became easy.
d. There was a distinction between instructions and data.
e. Programs could be easily understood.
a) Because a computer does not understand symbolic language, it has to be translated to machine language.
b) Like machine language, it is also machine dependent.
c) Knowledge of hardware required.
3) High-Level Language
This language is machine independent or hardware independent. Programming in high-level languages does not requires more knowledge of hardware and CPU.
High Level Languages were developed to :
a) Improve programmer efficiency
b) Shift focus from the computer to problem solving.
c) Develop portable applications.
a) Machine Independence
b) Easy to learn
c) Few errors
d) Low cost
e) Easy to maintain
Programs written in these type of language have lower efficiency as compared to the machine language. These programs result in multiple machine language instructions taking more time to execute and also require more memory space. But with the advent of efficient and optimizing compliers, this problem is almost non-existent now.
Q. ) Discuss Binary, Decimal, Octal and Hexadecimal number system in details. Explain BCD, EBCDIC, and ASCII Codes.
Decimal system is a base 10-system which means there are 10 distinct digit 0 through 9. The value that the digits represent depends on the “weights” or position they hold.
Every computer stores numbers, letters and other characters in a codes form. As mentioned earlier every character in storage is represented by a string of 0s and 1s. The numbering system in which these two digits are found is binary numbering system. The number system uses a base of 2 the possible symbols begin 0 and 1.
An binary system is a base 2 system, the position weights are used on the powers of 2.
Octal system was issued to provide a shorthand way to deal with the long strings of 1s and 0s created in binary. It is a base-8 system using digits 0 through 7. The position weights are based on the power of 8.
The Hexadecimal system is also used to provide a shorthand way to deal with long strings of 1s and 0s created in binary. It contains the digits 0 through 9 and the letters A through F. The letters are used because sixteen placeholders are needed and there are only ten distinct digits in the decimal system.
With BCD, it is possible to convert each decimal number into its binary equivalent rather than convert the entire decimal value into a pure binary form. A BCD equivalent of each possible decimal symbol is shown below.
Since 8 and 9 require 4 bits, all decimal digits are represented in BCD by 4 bits. When 4 bits are used, there are only 16 possible configurations (24).
These arrangements are not used in BCD coding. That is, 1111 does not represent 1510 in BCD. Instead, the proper BCD code for 1510 is 0001/0101.
ASCII and EBCDIC
Computer designers first used 6 bits, instead of using 4 bits with only 16 possible characters and then they moved onto 7 or 8 bits to represent characters in alphanumeric versions of BCD. With 6 bits, it only possible to represent 64 different characters (26). The 7 bit ASCII is widely used in data communications work and is the code used to represent data internally in personal computer.
The 8 bit codes most codely used are :
i) Extended Binary Coded Decimal interchange code. This is used in IBM mainframe models.
ii) ASCII-8, This an 8 bit version of ASCII that is frequently used in larger machines.
Explain Analog Data Communication ? Communication Channel
Analog Data Communication
Analog data Transmission is the transmission of data in a continuous wave form as shown in fig. The telephone system, for instance, is designed for analog data transmission.
The Amplitude of a wave as the signal strength compared to some reference value. Analog signals are based upon amplitude, or strength, shifts which vary constantly form positive to negative values. Amplitude is commonly expressed in volts.
The Frequency of a wave is the time it takes for a wave to complete one cycle. In other work, if a signal takes one second to make a transition from high amplitude to low and back to high the frequency of the wave is one second. Frequency is typically measured in hertz(Hz). Or cycle per second.
The phase of a signal refers to the relative state of the wave when timing began. Signal phase is measured in degrees.
As with digital signals, analog signals can be modulated or encoded to presents binary data.
Digital Data Transmission
Digital Data Transmission is the transmission of data using distinct “ON” and “OFF” electrical states. Computer circuitry represents data as a pattern of “ON” and “OFF” electrical states. These two states are represented by a 1 for “ON” and O for “OFF”. Digital data communication as shown in fig. All the data communication between the computer is in digital form as the computers understand and work only in digital forms.
Modem is used to bridge the gap between digital and analog data transmission, or to allow the digital data to be transmitted/received over from the telephone lines