Data representation

Question 1

Why do computers use binary ?

Answer 1

• Computers only recognise one and zero
• It is à base to the number system
• incredibly efficient and effective way of storing information in a computer system

Question 2

What does the bit pattern ‘01000111’ represent

Answer 2

• The binary number of 71
• ASCII character ‘G’
• a single pixel of colour in an 8-bit depth colour-depth bitmap
• part of a digital sound file

Question 3

What does the decimal base system range from ?

Answer 3

0-9

Question 4

what does the binary base system range from ?

Answer 4

1,0

Question 5

What does hexadecimal range from ?

Answer 5

0-9 , and A-F

Question 6

When we use binary left shift what does the bit multiply by ?

Answer 6

By a factor of 2

Question 7

In binary right shift what does the number divide by ?

Answer 7

2

Question 8

How many bits do characters(letters) take up?

Answer 8

128/7Bits

Question 9

What is a character set?

Answer 9

A defined list of characters defined by the hardware and software

Question 10

What does ASCII stand for ?

Answer 10

American Standard Code For Information Interchange

Question 11

How many bits did ASCII have for character sets?

Answer 11

7Bits / 128

Question 12

How many bits does extended ASCII have ?

Answer 12

8bits/256

Due to foreign languages and useful efficient graphic symbols

Question 13

In ASCII what are characters 0-31 reserved for ?

Answer 13

Special characters and instructions for the computers

Question 14

What is Unicode?

Answer 14

Used for all the languages and emojis

Question 15

How many bit character set does Unicode have ?

Answer 15

24bit
However hexadecimal is used because 6digits in hexadecimal = 24 bits in binary .
Remember 1 nibble = 1hex digit

Question 16

What is metadata ?

Answer 16

Additional data stored with the image such as width ,height ,colour depth of the image

Question 17

In bitmap images not only does the metadata need to be stored but also …

Answer 17

The colour palette

Question 18

How do you convert hex to decimal?

Answer 18

In hex moving right to left place values multiplied in powers of 16
To convert from decimal to hex divide by 16

Question 19

How are images stored ?

Answer 19

As a series of pixels

Question 20

What is the colour depth ?

Answer 20

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

Question 21

How do you work out how many colours there are in an image ?

Answer 21

Total number of colours = 2(subscript)n (number of bits per pixel)

Question 22

What is the image resolution ?

Answer 22

The image resolution is the number of pixels in the image. it sometimes given as width x height .The higher the resolution , the more pixels the image is made of , so the better quality of the image .

Question 23

How to work out how many bits an image will take up

Answer 23

File Size=image resolution x colour depth x =width x height x colour depth

Question 24

How is sound recorded as ?

Answer 24

Sound is recorded by a microphone as an analogue signal.
Analogie signals are piece of continuously changing data.
Analogue signals need to be converted into digital data so that computers can read and store sound files

Question 25

Why might you want to compress data

Answer 25

1. Smaller files take up less storage on a device
2. streaming and downloading files from the internet is quicker as they take up less bandwidth
3. allows web pages to load quicker
4. email services have restrictions on the size of attachments you can send , thus compressing them permits you to send the same content but in a smaller size.

Question 26

What are the differences between lossy and lossless compression?

Answer 26

1. Lossy compression works by permanently removing data from the file , which essentially limits the bits the file needs and so reduces its size
2. Lossless compression makes the file smaller by temporarily remo g the metadata and restoring it when the file is opened

Question 27

Why might you want to use lossy compression?

Answer 27

1. greatly reduced file sizes,meaning more files can be stored
2. less bandwidth is required to stream