Unit 2 - Data Representation

Question 1

What is the binary number system?

Answer 1

Computers use a binary number system consisting of only 0s and 1s. Everything a computer needs to process must be converted to a binary format.

Question 2

What is the order of file size from smallest to biggest?

Answer 2

Bit (b)
Byte (B)
Kilobyte (KB)
Megabyte (MB)
Gigabyte (GB)
Terabyte (TB)
Petabyte (PB)

Question 3

How much is is a bit?

Answer 3

A single 0 or 1.

Question 4

How much is a nibble?

Answer 4

4 bits

Question 5

How much is a byte?

Answer 5

8 bits - one character of text

Question 6

How much is a Kilobyte?

Answer 6

1000 bytes

Question 7

How much is a Megabyte?

Answer 7

1000 KB

Question 8

How much is a gigabyte?

Answer 8

1000 MB

Question 9

How much is a terabyte?

Answer 9

1000 GB

Question 10

How much is a petabyte?

Answer 10

1000 TB

Question 11

What is denary?

Answer 11

It is a base 10 number system with 10 digits 0-9

Question 12

What is an overflow?

Answer 12

The generation of a number that is too large to be represented by the device intended to store it.

Question 13

What is hexadecimal (or hex)?

Answer 13

A numerical system of notation that uses 16 rather than 10 as its base. The 16 hex base digits are 0 – 9 and the letters A – F.

Question 14

How would you convert hex to denary?

Answer 14

Multiply the left side by 16 and add the units.
For example 2D: 2*16 = 32…………..32 + D(13) = 45

Question 15

What are binary shifts?

Answer 15

Allows you to easily multiply or divide a base-2 binary number. A left shift multiplies the number by 2, while a right shift divides it by 2.

Question 15

Why use hex?

Answer 15

It’s much simpler to remember hex than binary. It is quicker to write, less likely to make an error, and easy to convert.

Question 15

How would you convert denary to hex?

Answer 15

Divide the denary by 16. This would give the left-hand hex digit. The remainder would be the units.

Question 16

What is ASCII?

Answer 16

ASCII (American standardised code for information interchange) is a character set devised for early telecommunication systems but proved to be ideal for computer systems. Uses 7 bits, providing 32 control codes and 96 displayable characters. The eighth bit is often used for error checking.

Question 17

What is Unicode?

Answer 17

Standard character set that replaces the use of multiple different character sets. Incorporates characters from almost all global languages. A 16-bit extension of ASCII.”

Question 18

What are the 5 different image file formats?

Answer 18

. BMP - Bitmap
. JPG -
. TIFF
. PNG
. GIF

Question 19

What are pixels?

Answer 19

The smallest unit of a digital image or graphic that can be displayed on a digital device. A pixel is represented by a dot or square on a computer display. Each pixel would have a colour represented by a binary number. The colour can change by changing the binary number.

Question 20

What is colour depth?

Answer 20

Colour depth, or bit depth, is the number of bits used for each pixel.
1 bit per pixel = 2¹ = 2 colours
2 bit per pixel = 2² = 4 colours
3 bit per pixel = 2³ = 8 colours
A higher bit depth gives us a greater range of colour and a better quality image.

Question 20

What is resolution?

Answer 20

Resolution is the concentration of pixels within a specific area. The area is defined by the image width and height in pixels.

Question 21

How would you calculate image file size?

Answer 21

The total size of an image file in storage. Size in bits = Width in pixels * Height in pixels * Colour depth in bits.

Question 22

What is metadata?

Answer 22

metadata is a collection of data that provides info about other data. This would include: . Bit depth in bits per pixel . Resolution . Data created . Author

Question 23

What is a bitmap graphic made up of?

Answer 23

It is made up of individual pixels.

Question 24

How must sounds be converted to so that it can be stored by a computer?

Answer 24

It must be converted from analogue to digital.

Question 25

What is sample rate?

Answer 25

The number of samples taken per second.

Question 26

What is sampling?

Answer 26

Sampling is the process whereby an analogue wave is converted into a digital signal.

Question 27

What is sample duration?

Answer 27

How many seconds of audio a sound file contains.

Question 28

What is image quality?

Answer 28

The overall detail of an image, affected by colour depth and resolution.

Question 29

What are samples measured in?

Answer 29

Hertz (Hz) 1 Hz = 1 sample per second

Question 30

What is sample resolution?

Answer 30

The number of bits used to record each measurement. More bits per sample enables the height of the wave to be more accurately measured, but this increases the file size.

Question 31

What is the formula to calculate sound file sizes?

Answer 31

File size (bits) = sample rate * resolution * seconds

Question 32

How does recording quality improve?

Answer 32

. The more frequently we sample the sound . The more accurately we record the wave height.

Question 33

What is lossy compression?

Answer 33

A compression method that generally involves a loss of quality where experience tells us that it will be least noticed. It permanently deletes part of the data and tries and reconstruct the file.

Question 34

What is lossless compression?

Answer 34

A compression method that allows a file to be recreated in its original quality. It leaves out repeated data and makes a note of how many times it is repeated.

Question 35

What are the benefits of compression?

Answer 35

. Download times are reduced . Voice can be transmitted fast enough to keep up with speech. . Reduces traffic over the internet . Quicker to complete transmission

Question 36

What is buffering?

Answer 36

This is caused when the download speed is slower than the playback speed.