Topic 3-Data representation

Question 1

What do computers use to represent all data and instructions?

Answer 1

Tiny switches called transistors and electric circuits.

Question 2

What are binary digits?

Answer 2

Bits, a nibble is 4 bits.

Question 3

What are hexadecimal used for?

Answer 3

They provide a human friendly representation of binary values and are quicker to write and type. It is also less likely for humans to make mistakes.

Question 4

What are binary shifts and how can they be used?

Answer 4

They can be used for simple division and multiplication and each number that goes out is discarded.

Question 5

What is largest number 5 bits can represent?

Answer 5

31 but it can do 32 letters.

Question 6

Why was ASCII created?

Answer 6

To standardise communication. 7 bits so 128 characters.

Question 7

Why was unicode created?

Answer 7

So not only the English language could be represented. Uses 4 bytes so around 138,00 characters. The first characters were the same as ASCII so old systems did not have to update.

Question 8

What is a picture element?

Answer 8

A pixel is the smallest element in an image.

Question 9

What is a group of pixels together called?

Answer 9

A bitmap.

Question 10

What is resolution?

Answer 10

The total number of pixels.

Question 11

What is colour depth?

Answer 11

A colour depth of 3 can store 8 colours for one pixel.

Question 12

What is RGB?

Answer 12

Used to combine light for more in depth pictures. 24 bits per colour so 8 for red, 8 for green and 8 for blue. This allows 256 colours. Charlie loves RGB.

Question 13

What are the types for bitmap images?

Answer 13

.JPG, .PNG, .BMP AND .TIFF

Question 14

How do you calculate the file size of an image?

Answer 14

Resolution x colour depth

Question 15

What are vector graphics?

Answer 15

Creating an image with vector coordinates(pixels can not always be seen).

Question 16

What are the pros and cons of vector graphics?

Answer 16

+can never see pixels
+smaller file size for same image
+amazing for simple, small or large images
-terrible for realistic images

Question 17

What is analogue sound?

Answer 17

Sound waves travel through vibrations in the air.

Question 18

What is the amplitude?

Answer 18

The height of the sound wave. The higher the amplitude, the higher the sound.

Question 19

What is the pitch?

Answer 19

Closer together waves means higher pitch and frequency.

Question 20

What is an ADC?

Answer 20

Analogue to digital converter.

Question 21

What is a sample rate?

Answer 21

Number of measurements taken per second(Hz).

Question 22

What does the bit depth mean for sounds?

Answer 22

Higher bit depth means higher resolution of sound.

Question 23

How do you calculate file size for sound.

Answer 23

seconds x bit depth x sample rate

Question 24

What frequency can babies hear?

Answer 24

20-20,000.

Question 25

What protocol does facetime use?

Answer 25

Voice over internet protocol(VOIP).

Question 26

What is MIDI?

Answer 26

Digital interface for sound that is more consistent and can represent music with instructions. Notes do not fade.

Question 27

What is metadata?

Answer 27

Data about data.

Question 28

Why are files compressed?

Answer 28

To reduce download and upload speed for faster transmission and less data errors.

Question 29

What is lossy compression?

Answer 29

Removes useless information such as frequencies humans cannot hear or a shade we won’t notice. 10-2-6. File cannot be fully restored.

Question 30

What is losless compression?

Answer 30

No data is lost. Done by RLE(run length encoding) or huffman trees(not always good as huffman tree has to be sent too). 10-4-10.

Question 31

RLE example. 1101000

0011110

Answer 31

21 10 11 30

20 41 10

Question 32

What side is 0 on for huffman trees?

Answer 32

Left.