Lec 2 computer basics
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1) A computer accepts data as input, processes it according to programmed instructions, and produces output which it can store for future use. 2) Data is represented by characters like letters, numbers and symbols that can be interpreted by humans or computers. Information is organized data that has meaning. 3) Common computer input devices include keyboards, mice, scanners, and microphones. Output devices display or print the results of processing and include monitors, printers, and speakers.
Lec 2 computer basics
- 2. Definition Computer is an electronic device that takes raw data as input from the user and process these data under control of set of instructions(called program) and gives the result as output and save output for future use.
- 3. What is Data? Data can be defined as a representation of facts, concepts or instructions in a formalized manner, which should be suitable for communication, interpretation or processing by human or electronic machine. Data is represented with the help of characters like alphabets (A-Z, a-z), digits (0-9) or special characters(+,-,/,*,<,>,=, etc.).
- 4. Information is organised or classified data so that it has some meaningful values to the receiver. Information is the processed data on which decisions and actions are based. For the decision to be meaningful, the processed data must qualify the following characteristics: Timely - Information should be available when required. Accuracy - Information should be accurate. Completeness - Information should be complete.
- 5. 1) Accepts data Input 2) Process data Processing 3) Produces output Output 4) Stores result Storage
- 6. Data processing is the re-structuring or re- ordering of data by people or machine to increase their usefulness & add values for particular purpose. Data processing consists of basic steps input, processing and output. These three steps constitute the data processing cycle.
- 7. Input - In this step, the input data are prepared in some convenient form for processing. The form will depend on the processing machine. For example, when electronic computers are used, the input data could be recorded on any one of several types of input mediums, such as magnetic disks, tapes and so on. Processing - In this step, input data are changed to produce data in a more useful form. For example, pay-checks may be calculated from the time cards or a summary of sales for the month may be calculated from the sales orders.
- 8. Output -Here, the results of the proceeding processing step are collected. The particular form of the output data depends on the use of the data. For example, output data may be pay-checks for employees.
- 9. All of the components of a computer system can be summarized with the simple equations. Computer system = Hardware +Software+User Hardware = Internal devices + Peripheral devices All physical parts of the computer( or everything we can touch) are known as hardware. Software = Programs Software gives “intelligence” to computer.
- 10. Following list demonstrates the advantages of Computers in today's arena. High Speed Computer is a very fast device. It is capable of performing addition of very big data. The computer has units of speed in microsecond, nanosecond and even the picosecond. It can perform millions of calculations in a few seconds as compared to man, who can spend many months for doing the same task.
- 11. Accuracy In addition to being very fast, computers are very accurate. The computer has performed calculations 100% error-free. Computers perform all jobs with 100% accuracy. Storage Capability The computer has much more storage capacity than human beings. It can store large amount of data. It can store any type of data such as images, videos, text, audio and any other type.
- 12. Diligence Unlike human beings, a computer is free from monotony, tiredness and lack of concentration. It can work continuously without creating any error and boredom. It can do repeated work with same speed and accuracy. Versatility A computer is a very versatile machine. A computer is very flexible in performing the jobs to be done. This machine can be used to solve the problems relating to various different fields. At one instant, it may be solving a complex scientific problem and the very next moment it may be playing a card game.
- 13. Reliability A computer is a reliable machine. Modern electronic components have failure-free long lives. Computers are designed to make maintenance easy. Automation Computer is an automatic machine. Automation means ability to perform the task automatically. Once a program is given to computer, i.e., stored in computer memory, the program and instructions can control the program execution without human interaction.
- 14. Reduction in Paper Work The use of computers for data processing in an organization leads to reduction in paper work and speeds up the process. As data in electronic files can be retrieved as and when required, the problem of maintenance of large number of files gets reduced.
- 15. No IQ A computer is a machine and has no intelligence of its own to perform any task. Each and every instruction has to be given to the computer. A computer can not take any decision on its own. Dependency It can perform function as instructed by user, so it is fully dependent on human being.
- 16. Environment The operating environment of computer should be dust-free and suitable to it. No Feeling Computer has no feeling or emotions. It cannot make judgement based on feeling, taste, experience and knowledge unlike a human being.
- 17. In computing, an input device is any peripheral (piece of computer hardware equipment) used to provide data and control signals to an information processing system such as a computer or other information appliance.
- 18. Keyboard Most common and very popular input device is keyboard. The keyboard helps in inputting the data to the computer. The layout of the keyboard is like that of traditional typewriter, although there are some additional keys provided for performing some additional functions. Keyboards are of two sizes 84 keys or 101/102 keys, but now 104 keys or 108 keys keyboard is also available for Windows and Internet.
- 19. 1.Typing Keys-These keys include the letter keys (A- Z) and digits keys (0-9) which generally give same layout as that of typewriters. 2. Numeric Keypad- It is used to enter numeric data or cursor movement. Generally, it consists of a set of 17 keys that are laid out in the same configuration used by most adding machine and calculators. 3. Function Keys-The twelve functions keys are present on the keyboard. These are arranged in a row along the top of the keyboard. Each function key has unique meaning and is used for some specific purpose.
- 20. 4.Control keys- These keys provide cursor and screen control. It includes four directional arrow key. Control keys also include Home, End, Insert, Delete, Page Up, Page Down, Control(Ctrl), Alternate(Alt), Escape(Esc). 5. Special Purpose Keys- Keyboard also contains some special purpose keys such as Enter, Shift, Caps Lock, Num Lock, Space bar, Tab, and Print screen.
- 21. Mouse Mouse is most popular Pointing device. It is a very famous cursor-control device. It is a small palm size box with a round ball at its base which senses the movement of mouse and sends corresponding signals to CPU on pressing the buttons. Generally, it has two buttons called left and right button and scroll bar is present at the mid. Mouse can be used to control the position of cursor on screen, but it cannot be used to enter text into the computer.
- 22. Advantages Easy to use Not very expensive Moves the cursor faster than the arrow keys of keyboard.
- 23. Joystick Joystick is also a pointing device, which is used to move cursor position on a monitor screen. It is a stick having a spherical ball at its both lower and upper ends. The lower spherical ball moves in a socket. The joystick can be moved in all four directions. The function of joystick is similar to that of a mouse. It is mainly used in Computer Aided Designing (CAD) and playing computer games.
- 24. Light Pen Light pen is a pointing device, which is similar to a pen. It is used to select a displayed menu item or draw pictures on the monitor screen. It consists of a photocell and an optical system placed in a small tube. When light pen's tip is moved over the monitor screen and pen button is pressed, its photocell sensing element, detects the screen location and sends the corresponding signal to the CPU.
- 25. Scanner Scanner is an input device, which works more like a photocopy machine. It is used when some information is available on a paper and it is to be transferred to the hard disc of the computer for further manipulation. Scanner captures images from the source which are then converted into the digital form that can be stored on the disc. These images can be edited before they are printed.
- 26. Microphone Microphone is an input device to input sound that is then stored in digital form. The microphone is used for various applications like adding sound to a multimedia presentation or for mixing music.
- 27. Magnetic Ink Card Reader (MICR) MICR input device is generally used in banks because of a large number of cheques to be processed everyday. The bank's code number and cheque number are printed on the cheques with a special type of ink that contains particles of magnetic material that are machine readable. This reading process is called Magnetic Ink Character Recognition (MICR). The main advantage of MICR is that it is fast and less error prone.
- 28. Optical Character Reader (OCR) OCR is an input device used to read a printed text. OCR scans text optically character by character, converts them into a machine readable code and stores the text on the system memory.
- 29. Bar Code Readers Bar Code Reader is a device used for reading bar coded data (data in form of light and dark lines). Bar coded data is generally used in labelling goods, numbering the books, etc. It may be a hand-held scanner or may be embedded in a stationary scanner. Bar Code Reader scans a bar code image, converts it into an alphanumeric value, which is then fed to the computer to which bar code reader is connected.
- 30. Optical Mark Reader (OMR) OMR is a special type of optical scanner used to recognize the type of mark made by pen or pencil. It is used where one out of a few alternatives is to be selected and marked. It is specially used for checking the answer sheets of examinations having multiple choice questions.
- 31. An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) which converts the electronically generated information into human-readable form.
- 32. Following are few of the important output devices, which are used in Computer Systems: Monitors Graphic Plotter Printer
- 33. Monitors Monitor commonly called as Visual Display Unit (VDU) is the main output device of a computer. It forms images from tiny dots, called pixels, that are arranged in a rectangular form. The sharpness of the image depends upon the number of the pixels. There are two kinds of viewing screen used for monitors: Cathode-Ray Tube (CRT) Flat-Panel Display
- 34. Cathode-Ray Tube (CRT) Monitor In the CRT, display is made up of small picture elements called pixels for short. The smaller the pixels, the better the image clarity or resolution. It takes more than one illuminated pixel to form whole character, such as the letter 'e' in the word help. A finite number of characters can be displayed on a screen at once. The screen can be divided into a series of character boxes - fixed location on the screen where a standard character can be placed. Most screens are capable of displaying 80 characters of data horizontally and 25 lines vertically.
- 35. There are some disadvantages of CRT: Large in Size High power consumption
- 36. Flat-Panel Display Monitor The flat-panel display refers to a class of video devices that have reduced volume, weight and power requirement compared to the CRT. You can hang them on walls or wear them on your wrists. Current uses for flat-panel displays include calculators, video games, monitors, laptop computer, graphics display. The flat-panel display are divided into two categories: Emissive Displays - The emissive displays are devices that convert electrical energy into light. Example are plasma panel and LED (Light-Emitting Diodes). Non-Emissive Displays - The Non-emissive displays use optical effects to convert sunlight or light from some other source into graphics patterns. Example is LCD (Liquid-Crystal Device)
- 38. Printers Printer is the most important output device, which is used to print information on paper. There are two types of printers: Impact Printers Non-Impact Printers
- 39. Impact Printers The printers that print the characters by striking against the ribbon and onto the paper, are called impact printers. Characteristics of Impact Printers are the following: Very low consumable costs Impact printers are very noisy Useful for bulk printing due to low cost There is physical contact with the paper to produce an image
- 40. These printers are of two types: Character printers Line printers Character Printers: Character Printers are printers, which print one character at a time. These are of further two types: Dot Matrix Printer (DMP) Daisy Wheel
- 41. Dot Matrix Printer In the market, one of the most popular printer is Dot Matrix Printer because of their ease of printing features and economical price. Each character printed is in form of pattern of Dot's and head consists of a Matrix of Pins of size(5*7, 7*9, 9*7 or 9*9) which comes out to form a character that is why it is called Dot Matrix Printer.
- 42. Advantages Inexpensive Widely Used Other language characters can be printed Disadvantages Slow Speed Poor Quality
- 43. Daisy Wheel Head is lying on a wheel and Pins corresponding to characters are like petals of Daisy (flower name) that is why it is called Daisy Wheel Printer. These printers are generally used for word-processing in offices which require a few letters to be send here and there with very nice quality representation. Advantages More reliable than DMP's Better quality The fonts of character can be easily changed
- 44. Disadvantages Slower than DMP's Noisy More expensive than DMP's
- 45. Line Printers Line printers are printers, which print one line at a time. These are of further two types: Drum Printer Chain Printer
- 46. Drum Printer This printer is like a drum in shape so it called drum printer. The surface of drum is divided into number of tracks. Total tracks are equal to size of paper, i.e., for a paper width of 132 characters, Drum will have 132 tracks. A character set is embossed on track. The different character sets available in market are 48 character set, 64 and 96 characters set. One rotation of drum prints one line. Drum Printers are fast in speed and prints between 300 to 2000 lines per minute.
- 47. Advantages Very high speed Disadvantages Very expensive Characters fonts can not be changed
- 48. Chain Printer In this printer, chain of character sets are used so it called Chain Printers. A standard character set may have 48, 64, 96 characters. Advantages Character fonts can easily be changed. Different languages can be used with the same printer.
- 49. Disadvantages Noisy Do not have the ability to print any shape of characters.
- 50. The printers that print the characters without striking against the ribbon and onto the paper are called Non-impact Printers. These printers print a complete page at a time, also called as Page Printers. These printers are of two types: Laser Printers Inkjet Printers
- 51. Laser Printers These are non-impact page printers. They use laser lights to produce the dots needed to form the characters to be printed on a page. Advantages Very high speed. Very high quality output. Gives good graphics quality. Supports many fonts and different character sizes.
- 52. Disadvantage Expensive. Cannot be used to produce multiple copies of a document in a single printing.
- 53. Inkjet Printers Inkjet printers are non-impact character printers based on a relatively new technology. They print characters by spraying small drops of ink onto paper. Inkjet printers produce high quality output with presentable features. They make less noise because no hammering is done and these have many styles of printing modes available. Colour printing is also possible. Some models of Inkjet printers can produce multiple copies of printing also.
- 54. Advantages High quality printing More reliable Disadvantages Expensive as cost per page is high Slow as compared to laser printer