AQA A LEVEL COMPUTER SCIENCE PAPER 2 EXAM QUESTIONS WITH CORRECT ANSWERS

AQA A LEVEL COMPUTER SCIENCE PAPER 2 EXAM QUESTIONS WITH CORRECT ANSWERS What is the principle of operation of a digital camera? - ANSWER -1) Shutter opens to let light onto a sensor at the back of the lens 2) RGB filters are used with different sensors in the camera to separate light 3) Intensity of each colour falling on a sensor is stored to form an RGB value What are some issues that can lead to data transmission errors? - ANSWER -- Electrical Interference - Power surges - Synchronisation issues - Physical issues with cables/connectors How are parity bits used? - ANSWER -- Used for detecting whether or not there has been an error in the data - 1) either odd ore even parity can be used to 'complete' the data 2) If the wrong number of bits are 'on' e.g. states even parity, shows odd parity an error has ocured 3) Receiving computer notifies the transmitting end and the data is resent How is Majority voting used? - ANSWER -Each bit of the data is sent multiple times, the correct bit is the one that appears most out of the three How are Check digits used? - ANSWER -- A single digit is calculated from all other digits in a string of digits, using a set method, and appended on the end of the string - Used to check for mistakes in input or transmission How are checksums used? - ANSWER -Data representing the number of bytes being sent is sent along with the actual data to ensure that all data has been received What are some potential flaws with error detection/correction methods ? (e.g. parity bits, majority voting, checksums) - ANSWER -- Parity bits: The switching of two bits would leave the error undetected - Majority voting: most of all storage and transmission of the data will be for redundancies - Check sum: The checksum data could become corrupted or lost in transmission What is the principle of operation of a Barcode? - ANSWER -- Laser light is directed at the barcode.