Unit 3 - Data

Question 1

What is the symbol for a set of values of integers?

Answer 1

Z

Question 2

What is the symbol for a set of values of irrational numbers?

Answer 2

Q

Question 3

What is an ordinal number?

Answer 3

A number describing the position of something

Question 4

What is ASCII?

Answer 4

Binary values used to encode the English alphabet.

Question 5

Advantages and disadvantages of using Unicode to ASCII

Answer 5

Unicode uses 4 bytes to represent every value, this means that it has the power to store more values therefore broadening the characters to values such as emojis. However, this requires more memory and storage space.

Question 6

Name a technique that can be used to check for transmission errors.

Answer 6

Parity bits, Check bits, Majority voting or Checksums

Question 7

What is a parity bit?

Answer 7

Is a bit that is set to odd or even on the transmitting end of the byte. When data is sent the parity is checked at the recieving end. If the wrong number of bits are on then an error has occured.

Question 8

What is a check digit and name an example of one time it is used in every day life?

Answer 8

A check digit is an additional digit added to the end of a string designed to check for mistakes in transmission. Used in barcodes using a special formula.

Question 9

What is a checksum?

Answer 9

Works similarly to a check digit, a sum of all bytes is calculated and the computer determines whether this is faulty or not.

Question 10

3 steps to convert a value to two’s complement:

Answer 10

1. Using decimal value find the binary value
2. Flip the bits around
3. Add one to the value

Question 11

Define resolution

Answer 11

Number of pixels used to make up a bitmap image

Question 12

Formula to work out image file size.

Answer 12

Resolution x colour depth

Question 13

Lossless vs Lossy compression

Answer 13

Lossless doesn’t remove any data but instead using pattern recognition, data is grouped together whilst lossy compression just removes less needed data.

Question 14

What is run length encoding?

Answer 14

When you have multiple of the same data you group it as the amount of that data then the actual data value.

Question 15

How is analogue sound recorded?

Answer 15

Using a microphone which takes the analogue input, this data is sent to the Analogue to Digital converter (ADC) which converts to digital sound and stored in binary.

Question 16

How to calculate file size of an audio file?

Answer 16

sample rate x length of audio in seconds x resolution

Question 17

Explain Nyquist’s theorem.

Answer 17

There is a limit on lowest sampling rate for an accurate recording. For this to be accurate samples need to be double the frequency.

Question 18

Benefits of MIDI

Answer 18

Only the instructions are sent and not the actual recorded sound,. resulting in smaller file size and increasing variety in which instrument can play the sound.