1.1.3 Data storage

Question 1

How is data stored in computers?

Answer 1

They are stored as 1s and 0s

Question 2

What are the 2 character representation systems?

Answer 2

ASCII which uses 8 bits for each character and Unicode which uses 16 bits for each character

Question 3

How are pictures represented?

Answer 3

Images are made of pixels and binary can be used to indicate colour. If we are given binary in a series we can use a grid to create an image. Metadata tells us the dimensions.

Question 4

How is sound stored?

Answer 4

Sound waves are converted into binary using sampling which records the wave at set intervals called sampling. If the set intervals

Question 5

What is data compression?

Answer 5

When the bit structure of a file is manipulated in such a way that a file will become smaller in size. Repeating data is moved permanently or temporary.

Question 6

What is lossy compression?

Answer 6

It refers to the way this method of compression works. In lossy compression data deemed unnecessary is removed in the process. Data is permanently removed file size reduced. Usually for multimedia. Done in streaming files.

Question 7

What is lossless compression?

Answer 7

Lossless compression refers to method of compression as no data is lost. Used when essential data that none can be lost. Many techniques but most use a shorthand to store data and can be reconstructed when opened.

Question 8

List some file types and their extensions and use:

Answer 8

Text:
.doc word doc
.rtf rich text
.pdf portable document

Data:
.csv Comma separated values
.xls Excel

Audio:
.wav wave
.mp3 audio

Video:
.mp4
.flv flash video

Image:
.bmp bitmap
.gif graphical interchange format
.jpg jpeg

Question 9

List some error checking methods and describe them;

Answer 9

• Systems that use even parity have even number of ones otherwise the parity bit is a 1 to make it even or there must be an error if it is not even
• ARQ is another method using acknowledgement and a timeout to confirm that data received otherwise it is sent again
• Checksum Data sent in blocks with an additional value at end of block Checksum is = to value of block is below 255 otherwise it is divided by 256 round to nearest number multiply by 256 difference of that and original value is checksum
• Echo check when data sent to receiver and then resent to compare
• Check digit