Data representation

Question 1

Character set

Answer 1

Character sets are collections of characters that a computer recognises from their binary representation

Question 2

AscII

Answer 2

Each ASCII character is given a 7-bit binary code - this means it can represent a total of 128 different characters,

Question 3

Unicode

Answer 3

Unicode tries to cover every possible letter that might be written. Unlike ASCII, Unicode uses multiple bytes for each character.

Question 4

Colour depth

Answer 4

The colour depth is the number of bits used for each pixel

Question 5

Image resolution

Answer 5

image resolution is the number of pixels in the image.

Question 6

Metadata

Answer 6

Information stored in an image file which helps the computer recreate the image on screen from the binary data in each pixel.

stores
the type of file
file size
height

Question 7

Data compression

Answer 7

Data compression is when we make file sizes smaller, while trying to make the compressed file as true to the original as possible.

Question 8

Compressing data files uses

Answer 8

Smaller files take up less storage space on a device.

Streaming and downloading files from the Internet is quicker as they take up less bandwidth.

Question 9

Lossy compression

Answer 9

Lossy compression works by permanently removing data from the file

-this limits the number of bits the file needs and so reduces its size.

Question 10

Lossless compression

Answer 10

Lossless compression makes the file smaller by temporarily removing data to store the file and then restores it to its original state when it’s opened.

Question 11

Advantages of lossy

Answer 11

Greatly reduced file size, meaning
more files can be stored.

Lossy files take up less bandwidth

Question 12

Disadvantages of lossy

Answer 12

Lossy compression loses data-the file can’t be turned back into the original.

Question 13

Lossless advantages

Answer 13

Data is only removed temporarily so there is no reduction in quality -the compressed file should look or sound like the original.

Lossless files can be decompressed

-turned back into the original.

Question 14

Disadvantages of lossless

Answer 14

Only a slight reduction in file size, so lossless files still take up quite a bit of space on your device

Question 15

Sound

Answer 15

Sound is Sampled and stored Digitally .
Sound is recorded by a microphone as an analogue signal.

Question 16

Analogue

Answer 16

Analogue signals are pieces of continually changing data.

2) Analogue signals need to be converted into digital data so that computers can read and store sound files. This is done by analogue to digital converters,

Question 17

how sampling is used for storing sound

Answer 17

Height of waveform is sampled
 Converted to digital
 Sample taken at a regular interval

Question 18

Sample rate

Answer 18

Sample rate (or sampling frequency) is how many samples you take in a second

Question 19

Bit depth

Answer 19

Bit depth is the number of bits available for each sample

Question 20

What happens if we increase the sample rate

Answer 20

the analogue recording is sampled more often. The sampled sound will be better quality and will more closely match the original recording.

Question 21

Increasing the bit depth

Answer 21

Increasing the bit depth means the digital file picks up quieter sounds, even if they’re happening at the same time as louder ones. This will also result in a sampled sound that is closer to the quality of the original recording

Question 22

2 functions of an operating system

Answer 22

user management
* allows the setting up of accounts
* security / setting of password
* set different access rights

• file management
• creation/editing/renaming of files and folders
• movement of files/folders

Question 23

quad core problem

Answer 23

 Software may be designed to run on 1 core and not
multiple cores
…some tasks cannot be split across cores
 Clock speed also affects speed