Computing Unit 3 5.0 / 5 based on 1 rating ? ComputingData representationASAQA Created by: Issy.edgeCreated on: 07-06-18 10:44 What are natural numbers (N)? 'Counting numbers' - any whole, positive number. E.g. 1,2,3,4... 1 of 25 What are integers (Z)? Any positive or negative whole number. E.g. -3,-2,-1,0,1,2,3... 2 of 25 What are rational numbers (Q)? Any integers or value that can be expressed as a fraction or ratio. E.g. 2/3, 5, -10, 0.1... 3 of 25 What are irrational numbers? Any number that can't be expressed as a fraction. E.g. pi, root 2.... 4 of 25 What are real numbers (R)? Any rational or irrational number. 5 of 25 What are ordinal numbers? A 'place number'. E.g. 1st, 4th.... 6 of 25 What problems can cause data to be transmitted incorrectly? Electrical interference, power surges, synchronisation issues, wear + tear on cables or connectors. 7 of 25 How are parity bits used? Uses either odd or even parity, the parity bit is either set to a 1 or 0 to make the total sum of each number either odd or even. 8 of 25 How is majority voting used? Each bit of a message is sent 3 times and the most commonly sent bit is assumed to be the correct one. 9 of 25 How are check digits used? An extra digit is added at the end of a long number, errors are checked for using the modulo 10 system. 10 of 25 How is checksum used? A total sum of all bytes in the data is calculated and sent as well, sum is recalculated after being received and checked against original. 11 of 25 What is an overflow error? Can happen when adding binary numbers, there is an extra bit after they are added that can't fit into the fixed size space. 12 of 25 How do you use 2's complement? Find the positive binary value, switch all of the bits and then add 1 to the result to find the negative version. 13 of 25 What is the resolution of a digital image? This defines the number of pixels used to make up a bitmap, doesn't define the actual size of the image. 14 of 25 How do you calculate file size for a digital image? File size = pixels x bit depth 15 of 25 What is metadata? This is data about the data being saved. E.g. date created, colour depth, no. of pixels... 16 of 25 How do you convert from analogue to digital sound? Analogue sound samples are taken, each sample is quantised and translated to an integer, integers are converted and stored as binary. 17 of 25 How do you calculate file size for digital sound? File size = sample rate x resolution x length (in seconds) 18 of 25 What is the Nyquist theorom? Samples must be twice the highest frequency. 19 of 25 What is lossy compression? Non - essential data is permanently removed, quality decreases, file transfer is faster. 20 of 25 What is lossless compression? Patterns in the data are summarised, the original data can be rebuilt, file transfer is slower. 21 of 25 What is encryption? A way of coding data so it can't be understood without the means to decrypt it. (Keeps privacy) 22 of 25 What are the ways of decrypting coded data? Brute force attack (trying every possible combination), frequency analysis (uses the letters that appear most and least often). 23 of 25 What is the Caesar cipher? Most basic encryption, shifts the letters of the alphabet by a certain number. 24 of 25 What is the Vernam cipher? The only cipher proven to be unbreakable, the key must be truly random and deleted after use. 25 of 25
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