Data Representation and validation

Question 1

What are the 2 factors effecting the file size of an image?

Answer 1

• Colour depth

- Image Resolution (The amount of pixels in an image)

Question 2

What is the colour depth and how do you work out the amount of colours possible?

Answer 2

The amount of bits in a pixel which represents a colour. The more bits there are, the more colours can be displayed
2^bitDepth= possible colours
- 4 bit colour depth 16 colours (2^4)
-8 bit colour depth = 256 (2^8)

Question 3

How do you work out the file size of an image?

Answer 3

Resolution (pixels on X axis × pixels on Y axis) x colour depth = file size

Question 4

How is image data stored?

Answer 4

They are stored in files where binary data is placed into a bit map.

Question 5

Why do some image files have more bytes than expected?

Answer 5

Metadata such as:

• Data when photo was taken
• Name of file
• Location of take image
• details of the image

Question 6

What is the difference between analogue and digital sound waves?

Answer 6

Analog- Continuous and ‘smooth’

Digital- Discrete and a measurement of analogy waves

Question 7

What are the audio converters?

Answer 7

ADC - Analog-to-Digital Converter

DAC- Digital-to-Analog Converter.

Question 8

What the 3 factors affecting the file size of an audio file?

Answer 8

• Sample resolution (Audio Bit depth)
• Sample rate (Amount of analogue readings taken per second- 1hz = 1 sample per second)
• Seconds of audio

Question 9

How do you calculate audio file size?

Answer 9

Audio bit depth (bits) x Hertz (Hz) x seconds = File Size (bytes)

Question 10

What are the data types (6) and examples?

Answer 10

Integers (1,2,3,4..)
Characters (A,#,8,@)
String  ("Hello World")
Real (3.141)
Date (21/05/2022)
Boolean (True/False)

Question 11

What is the difference between Validation and Verification?

Answer 11

Validation- When code is used to check that data entered into a system is reasonable, sensible and legal (If it’s valid)

Verification- When users the check the data in the system to check it perfectly matches the source of data (E.g. Questionnaire results)

Question 12

What are the 5 validation checks?

Answer 12

Type - (Checks data type)
Format - (Checks pattern)
Length - (Checks length/ number of character required)
Presence - (Checks Entered and not blank)
Range - (Checks Upper and low boundaries)

Question 13

What are the 3 Verification checks?

Answer 13

• Proof Reading
• Double entry of data (Check if they are the same)
• Sending back printouts

Question 14

What does a type check do?

Answer 14

Checks the right type of data is being entered

Question 15

What does a format check do?

Answer 15

Checks the data being entered is the right pattern (e.g. Postcode = LLNN NLL)

Question 16

What does a length check length do?

Answer 16

Checks the data being entered is the right length or number of characters required (Not too little or too many)

Question 17

What does a presence check do?

Answer 17

Checks data has been entered and not left blank

Question 18

What does a range check do?

Answer 18

Checks boundaries to make sure data falls between an upper and lower value.

(E.g. Month of the data of birth must fall between 1 and 12)

Question 19

What are the two characteristics of data structures?

Answer 19

• Static/ dynamic (Scalability)

- Mutable/ immutable (Editability)

Question 20

What is the difference between a static and dynamic data structures?

Answer 20

Static- When a data structure is of a fixed size (E.g. An array)

Dynamic- When a data structure can grow and shrink (E.g. Lists)

Question 21

What is the difference between a mutable and immutable data structure?

Answer 21

Mutable- Allows a structure to be edited (E.g. An Array)

Immutable- A structure where data can out be changed, only added. (E.g. String)

Question 22

What is the correct name for a word document?

Answer 22

A Word Processor (package)

Question 23

What is the correct name for a excel?

Answer 23

A Spreadsheet

Question 24

What is the correct name for photoshop/ paint?

Answer 24

Image manipulator

Question 25

What is the correct name for a PowerPoint?

Answer 25

Presentation software

Question 26

What are the two types of compression?

Answer 26

Lossy and Lossless

Question 27

What happens in Lossless compression?

Answer 27

It finds groups of repeating data and records the data along with the number of times it was repeated

Question 28

What happens in lossy compression?

Answer 28

Removes some of the data and reconstructs it in a way to try and hide the lost data usually by averages. Data loss is irreversible.

Question 29

What are the files types that use Lossy compression?

Answer 29

JPG
GIF
MP3

Question 30

What are the files types that use Lossless compression?

Answer 30

PNG

TIF

Question 31

What asci number does the capital letters start and the lower case letters?

Answer 31

Capitals- 65

Lower case- 97

Question 32

How are images stored on a file?

Answer 32

Each coloured pixels position and colour can be stored in a bitmap. In a black and while image, a single bit can be used per pixel with 0 representing black and 1 white. For RGB images, the bit depth can be increased and more bits used to represent each colour in the image.

Question 33

How is sound stored on a file?

Answer 33

• Sound is sampled by converting analogues sound waves into digital waves that can be stored in a file.
• The frequency (Hz) of the samples can be increased as well as the amplitude (bit depth) of each sample to improve the quality of the sound.
• Different amplitudes can correspond different bit values per reading

Question 34

How is a string stored on a file?

Answer 34

Each character is converted into a binary number before being stored on the computer system which each correspond to it’s ascii character.