(Done) 1. Data Representation

Question 1

What is an overflow error

Answer 1

• When binary arithmetic gives you a result that requires more bits than the CPU is expecting

Question 2

What characters are contained within the alphanumeric alphabet

Answer 2

• Uppercase letters
• Lowercase letters
• Digits 0-9
• Symbols

Question 3

Define a character set

Answer 3

• Collections of characters that a computer recognises from their binary representation
• Character sets also contain special characters which do certain commands (e.g. enter and delete)

Question 4

List the character sets

Answer 4

• ASCII (American standard code for information exchange)
• Unicode

Question 5

Features of ASCII

Answer 5

• Most commonly used character set in the English speaking world
• Each ASCII character is given a 7 bit value (can have 128 characters)
• An extra bit is added to the beginning of the 7 bit value to make it fit nicely into 1 byte

Question 6

Features of unicode

Answer 6

• Tries to cover every possible character or symbol that might be written
• Uses multiple bytes for each character
• Covers all major languages, including ones with different alphabets
• The first 128 codes are the same as ASCII

Question 7

Define colour depth

Answer 7

• The amount of bits used for each pixel

Question 8

Define image reslution

Answer 8

• The number of pixels in the image

Question 9

Define metadata

Answer 9

• The information stored within a file which helps the computer recreate the image on screen from binary data for each pixel

Question 10

Information contained within metadata of an image

Answer 10

• File format
• Height
• Width
• Colour depth
• Resolution

Question 11

Define analogue signals

Answer 11

• Pieces of continuously changing data

Question 12

Define sampling

Answer 12

• The process of converting analogue to digital data

Question 13

What factors affect size and quality of sound files

Answer 13

• Sample rate
• Bit depth

Question 14

What is sample rate measured in

Answer 14

• Hz

Question 15

What is the calculation for file size

Answer 15

• File size = Sample rate x bit depth x duration

Question 16

Define data compression

Answer 16

• Making file sizes smaller, while trying to make the compressed files as true to the original as possible

Question 17

Uses of compression

Answer 17

• Smaller files take up less space
• Streaming and downloading files from the internet is quicker as they take up less bandwidth
• It allows web pages to load more quickly in web browsers
• Email services normally have restrictions on the size of the attachment you can send

Question 18

Define lossy compression

Answer 18

• Compression permanently removing data from the file, reducing the number of bits required therefore reducing it’s size

Question 19

Define lossless compression

Answer 19

• Makes the file smaller by temporarily removing data and restoring it once it is oppened

Question 20

Pros of lossy compression

Answer 20

• Greatly reduces file size meaning more files can be stored
• Lossy files take up less bandwidth so can be downloaded and streamed more quickly
• Commonly used - lots of software can read lossy files

Question 21

Cons of lossy compression

Answer 21

• Lossy compression loses data - the file can’t be turned back into the original
• Can’t be used on text and software files as theses need to retain all their original information
• Worse quality than the original however the difference is usually minimal

Question 22

Pros of lossless compretion

Answer 22

• Temporary size reduction - no reduction in quality
• Can be decompressed
• Can be used on text and software files

Question 23

Cons of lossless compresion

Answer 23

• Only small reduction in file size, still takes up a decent amount of space