Input devices. 1.Web-cam. _top Theory Notes for IGCSE. Image of web cam

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1 _top Theory Notes for IGCSE Input devices 1.Web-cam Image of web cam Definition: A digital video camera that is connected directly to a computer by USB cable or fixed if it is a lap-top. Unlike other digital cameras, a web-cam does not have memory. a) Live video conferencing b) Online personal chatting Advantages a) Promotes social online networking b) Saves the elderly and physically challenged people from traveling to meet distant people c) Saves costs for companies instead of traveling to hold meetings Disadvantages a) Initial cost of setting up equipment (video conferencing) is rather expensive b) Do not have memory, therefore it cannot store any pictures or videos c) Quality of distance objects in the room are limited since the web-cam is fixed d) It has limited features e) Pictures are often of poor quality compared to other digital cameras Go to Top of page

2 2 2. Microphone Image of microphone Device for inputting sound and video into the computer. A computer must have a sound card (ADC/DAC) for converting the sound or video from analogue to digital since a computer cannot read or store analogue data a) Used with Voice Recognition Software (VRS) to convert voice to text and issue voice commands b) Used with (VRS) to issue commands to computers, robotics, cars and other devices c) Used for opening doors for cars, hotels and banks d) For inputting speech and sound for use in presentations, music and films Advantages a) Faster than retyping documents b) More safe for drivers when operating car audio, lights and others Disadvantages a) You have to train the VRS during the initial stages b) VRS isn t as accurate as typing (e.g. can hardly distinguish words like there/their, where/were) c) Some VRS commands do not work well when the voice is affected by say, sore throat

3 3 3. Graphics Tablet Image of graphics tablet A slat device with a stylus pen used for free hand drawings NB: Do not confuse with an ordinary tablet/ipad a) Used in Computer Aided Design (CAD) applications such as fashion designs, architectural drafts, car designs, e.t.c. b) For drawings and computer graphics, such as advertising and marketing promotions c) For writing complex characters (e.g. Chinese and Japanese) Advantages a) Quicker to write complex characters than type (e.g. Chinese and Japanese) b) Possible to modify drawings before inputting into computer c) Produce more accurate drawings than with a mouse Disadvantages a) More expensive than other pointing devices such as mice b) Cannot type text

4 4 4. Light pen Image of light pen in use on a CRT monitor A pen with light sensors used for drawing and selecting screen objects. Currently works with CRT monitors. a) Drawing on screen (CAD) b) Selecting objects (or options) on CRT monitors Advantages a) Easier to use than a mouse b) Convenient to use with gloves hence a handy tool for medical surgeons c) Does not take much desk space due to its size d) Is not easily affected by dirt/stains and easier to clean than a mouse e) More accurate than touch screens Disadvantages a) Currently works with Cathode Ray Tube (CRT) monitors b) It has problems with slag/drag when drawing on screen c) Not very accurate when drawing d) Can easily get misplaced

5 5 Worksheet-A1 [25 marks] Please note that all answers are to be done on a separate page, preferably in a word processor. Ensure to number your answers correctly and remember to state the Worksheet name (e.g. Worksheet-A or B) 1. Define the following [4 marks] a) Microphone b) Web-cam c) Light pen d) Graphics tablet 2. Give 2 advantages of each of the following devices [8 marks] a) Graphics tablet b) Light pen c) Microphone d) Web-cam 3. Give 2 disadvantages of each of the following devices [8 marks] a) Graphics tablet b) Light pen c) Microphone d) Web-cam 4. Summarise the topic in your own words, in words [5 marks]

6 6 Worksheet-A2 [20 marks] 1. A medical surgeon prefers to use a light pen over other input devices (at his surgical desk). a) Why do you think he does so? Give 3 reasons [6 marks] b) Yousif spent last weekend doing some speech and sound recordings for his audio presentation on his computer. The next day he tried to load desktop publisher program in order to create invitation fliers, but the computer failed to load, saying Insufficient disk space i. What do you think happened to the space? [2 marks] ii. What consumes more disk space, audio or ordinary data files? [1 mark] iii. What name do we give to the device found in a sound card for converting analogue signal to digital before storage/reading by the computer? [1 mark] 2. Ruba has a desktop computer with an LCD screen. Recently she bought a light pen to use on her CAD drawings. However, she was advised to buy a CRT monitor instead. a) Why does she need a CRT monitor? Give one reason? [2 marks] 3. Mr. Zhen Zhiang is a Chinese newspaper reporter attending a conference while typing the news on a laptop computer in Chinese language. But he quickly switches to a graphics tablet. a) What is the advantage of graphics tablet over laptop? [2 marks] b) Why do you think drawing with a mouse is more difficult than using a graphics tablet? [2 marks] c) What name do we give to the pen used with a graphics tablet? [1 mark] 4. A microphone works with VRS applications to issue commands to computers, in some modern cars and some other household appliances. Some cars open doors at the instruction of the owner s voice only (not other people) a) What do you think would happen if the owner has a sore throat (assuming no one else s voice was not recorded)? [3 marks]

7 7 Input device continued 5) O.C.R (Optical character Recognition) Software that converts scanned hard copies into computer readable or editable format. They work with scanners. a) Converting scanned documents and photos so that they can be stored, edited or send across the network or internet b) Used in processing of passports and ID cards Advantages a) Quicker than other data entry devices like keyboard b) Faster than manually typing in data c) There is reduced errors since no manual data entry is involved Disadvantages a) Quality of scanned documents depends on quality of scanner b) One needs to have a scanner in order to use it c) It is not very accurate d) Cannot read handwriting e) Can be used to forge documents

8 8 6) O.M.R (Optical Mark Reader) Image of Optical Mark Reader (OMR) Image of shaded OMR form A device that works with special software to read multiple examination papers marked in pen or pencil. a) Read multiple examination papers b) Read questioners c) Read class registers d) Read consumer promotion and competition papers Advantages a) Quicker way of getting results of questioners or examination papers b) No typing, therefore more accurate c) More accurate than OCR Disadvantages a) If a form is not filled-in properly, the results are incorrect or its rejected b) Forms must be carefully designed c) Edges of the forms must not be folded, else it can be rejected or cause paper jam thus time consuming

9 9 MICR (Magnetic Ink Character Reader) Image of bank cheque showing MICR numbers Image of MICR device with bank cheque & card A device that reads special ink characters on bank cheques and other high security documents. a) Reading values and numbers on bank cheques before transfer into computer b) Reading highly confidential state security documents Advantages a) Less errors due to no manual input involved b) More secure than OCR since there is no alteration c) Ink characters can still be read even when over-written by ordinary ink Disadvantages a) More expensive than other direct entry methods used b) Not all character types can be read - limited.. Worksheet-B1 [25 marks] 1. List 2 uses of each of the following: [12 marks] a) OCR b) MICR OMR 2. Of the following, choose 2 and list 2 advantages of each [8 marks] 2 disadvantages of each [8 marks] a) MICR b) OMR OCR 3. Summarise the topic in your own words, in words [5 marks]

10 10 Worksheet-B2 [20 marks] 1a) What is the worst disadvantage of OCR in terms of crime? [2 marks] 1b) If you have a PC with OCR software, what other device do you need for OCR to work? [1 mark] 2. Up until the early 70 s, the University of Cambridge used to do marking of multiple choice exam papers in 2 months. But of late, 7000 sheets can be marked per hour. a) What device and software do you think they now use? [2 marks] b) What are 2 possible causes of rejected multiple choice exam papers when marked with OMR? [4 marks] c) In what sense is OMR more reliable and accurate than OCR? [2 marks] c) In a way, OMR devices are scanners, hence others are called Optical Mark Scanners. But why are they called optical? [2 marks] 3. Yousif and his brother Osama wanted to rob money (US$ ) from their father s foreign bank account. They designed a cheque and printed it with a colour printer. They forged their father s signature and presented the cheque to the bank teller the next day. The teller swiped the cheque in the MICR device and noticed something strange about the cheque and called their father. a) What do you think was the strange thing or missing on the cheque? [2 marks] d) Why do you think MICR devices are very expensive beyond the reach of the ordinary citizen? [2 marks] 4. In some modern schools, subject teachers use special forms as student registers for their respective subjects. At the end of the week the forms are fed into a certain device connected to a computer. The weekly records of students attendance are then sent by to the parents. a) What device is used to read these register forms? [1 mark] b) What 2 advantages does this method have? [2 marks]

11 11 Input devices continued 6) Sensors Sensors are devices that take measurements of a physical variable and input to a computer or any computer device. The physical data is analogue in nature, therefore it must be converted first to digital before being input to a computer. This is because computers are digital devices and as such they don t understand analogue data. The device that converts analogue data to digital is called Analogue to Digital Converter (ADC) and the one that converts digital data back to analogue in order for analogue devices like motors to understand is called, Digital to Analogue Converter (DAC). In most cases where sensors are connected to a computer device, you will find both ADC and DAC present. Classes of sensors a) Monitoring these trigger a warning b) Control these trigger an action Type of sensor Temperature sensor Automatic green-houses Medical field (i.e. hospitals) Environmental monitoring Domestic ovens Automatic washing machines Central heating systems Body temperature sensor Environmental & device sensors Pressure sensor Environment monitoring Robotics Automatic washing machines Medical field Burglar alarms Image of environmental pressure sensors Light sensors Blood pressure sensors Automatic doors Burglar alarms system Street lighting control Automatic green houses

12 12 Sound sensors Burglar alarms Monitoring liquid and powder flow in pipes during chemical processing Humidity sensors Super-computer/mainframe labs Factories such as for spraying or micro-chip manufacturing Environmental monitoring Automatic green-houses PH sensors Automatic green-houses Chemical processing plants Environmental control

13 13 Advantages of sensors a) Readings are continuous 24/7 they do not forget to take readings b) More accurate than human taken readings c) Because it is continuous it immediately triggers action (for control sensors) or warning (for monitoring sensors). d) System can be automated hence, no risk of human intervention thus becomes safe in hazardous areas like poisonous chemical processing plants or in areas that require precise and consistent control. Disadvantages of sensors a) Faulty sensors can give faulty results b) Dust or dirty can lead to false readings c) Reduces human interaction in the medical systems a patient in hospital would prefer to be attended to by a doctor rather than a medical system that does not comfort the patient Worksheet-C1 [25 marks] 1a) Define a sensor [2 marks] b) Sensor measurements are in what form in nature (analogue or digital)? [1 mark] c) Name 2 classes of sensors [2 marks] 2. List 2 uses of each of the following sensors: [10 marks] a) Light sensor b) Temperature sensor c) Humidity sensor d) Pressure e) PH 3a. Give 3 advantages of sensors [6 marks] 3b) Give 2 disadvantages of sensors [4 marks]

14 14 Worksheet-C2 [20 marks] 1. Sensors measure physical variables (e.g. temperature) over a continuous period. a) Why are they called variables? [2 marks] b)before a measurement is input to a computer, it is first converted to digital. Why is this done? [2 marks] c) what device converts the analogue signal to digital? [ 1mark] 2. From the sensors you have learnt, choose one and explain its use and what would happen if it becomes faulty [3 marks] 3.Temperature and blood pressure sensors are used in a medical system to measure, monitor and record a patient s body temperature and blood pressure levels for a whole month. The results are instantly processed by a computer and it produces graphs that are printed. a) List 4 advantages of such a system over human method [8 marks] b) List 2 disadvantages of such a system [4 marks] END