1.2 Memory And Storage (1.2.4 Data Storage)

Question 1

What is a character set?

Answer 1

A defined list of characters recognised by the computer

Question 2

Examples of character sets

Answer 2

ASCII and Unicode

Question 3

ASCII

Answer 3

• 7 bit binary code

- represents 128 different characters

Question 4

Unicode

Answer 4

• 24 bit character set

- covers all major languages

Question 5

Storing images

Answer 5

• stored as a series of pixels
• colour of each pixel is represented by a binary code
• more bits = more colours

Question 6

Colour depth

Answer 6

• colour depth is the number of bits used for each pixel
• most devices use a 24-bit colour depth
• number of pixels in the image is the image resolution

Question 7

File size (in bits)

Answer 7

Image resolution (width x height) x colour depth

Question 8

Metadata

Answer 8

• information stored in an image file

- e.g. file format, height, width, colour depth, and resolution

Question 9

Storing sound

Answer 9

• sound is recorded as an analogue signal
• analogue is converted into digital data
• this is called sampling

Question 10

Factors affecting size and quality of sound files

Answer 10

• sample rate

- bit depth

Question 11

Compressions

Answer 11

• lossy

- lossless

Question 12

Advantages of compressing data

Answer 12

• smaller files take up less storage space
• allows web pages to load more quickly in web browsers
• streaming and downloading files from the internet is quicker as they take up less bandwidth

Question 13

Lossy

Answer 13

• permanently removing data from file - lossy files are worse quality than the original
• takes up less bandwidth
• commonly used - lots of software can read lossy files
• examples are MP3 and JPEG

Question 14

Lossless compression

Answer 14

• makes file smaller by temporarily removing data to store the file
• no reduction in quality
• only a slight reduction in file size, so lossless files still take up space on a device
• examples are PNG and FLAC