Data

Question 1

What are the place value powers?

Answer 1

Powers of 2

e.g. 2^0, 2^1, 2^2

Question 2

What is an overflow error?

Answer 2

When a calculation produces a result that is greater than the computer can deal with

Question 3

Binary addition rules

Answer 3

0 + 0 = 0

1 + 0 = 1

1 + 1 = 0 (carry 1)

1 + 1 + 1 = 1 (carry 1)

Question 4

Logical shift rule

Answer 4

Move the bits as many times as specified and replace empty spaces at start/ end with 0s

Question 5

What is SIGN AND MAGNITUDE?

Answer 5

The leftmost bit is used to signify whether the number is positive or negative

0 = positive

1 = negative

Question 6

What is TWO’S COMPLEMENT?

Answer 6

Leftmost bit signifies whether the number is positive or negative

0 = positive

1 = negative (-128)

Replace the positive binary value 0s with 1s and vice versa and add 1 to find the two-s complement version

Question 7

How do you multiply signed binary numbers?

Answer 7

Use an arithmetic shift left (every shift multiplies by powers of 2)

Question 8

What is the rule with arithmetic shifts?

Answer 8

The most significant bit remains

e.g. a right shift by 2 of 10100101 = 11101001

Question 9

How do you divide signed binary numbers

Answer 9

Use an arithmetic shift right (every shift divides by powers of 2)

Question 10

Order of HEX values

Answer 10

1, 2, 3, 4, 5, 6, 7, 8, 9, A (10), B (11), C (12), D (13), E (14), F (15)

Question 11

How do you convert hex values to binary?

Answer 11

1) Split up the characters
2) Each character is represented by a number in denary
3) Each denary value can be written as a nibble
4) Join the nibbles together

e.g. C3 –> 12 = 1100 and 3 = 0011 SO 11000011 is C3

Question 12

What is ASCII?

Answer 12

Numbers assigned to text and characters using binary

Question 13

What is EXTENDED ASCII?

Answer 13

Uses 8 bits so that there are 256 code sequences

• Previously used 7 bits

Question 14

What is UNICODE?

Answer 14

Alternative to ASCII for other languages

An international encoding standard for use with different languages and scripts, by which each letter, digit, or symbol is assigned a unique numeric value that applies across different platforms and programs

Question 15

What is a PIXEL?

Answer 15

Short for ‘Picture Element’

The smallest single point of colour in a graphic image

Question 16

How do you work out IMAGE SIZE?

Answer 16

Total number of pixels

SO: number of pixels in width X number of pixels in height

Question 17

What is RESOLUTION?

Answer 17

The number of pixels per inch when the image is displayed

Question 18

What is COLOUR DEPTH?

Answer 18

The number of bits used to encode the colour of each pixel

The more bits used to encode colour, the greater the number of actual colours that can be represented

e.g. 1 bit = 2 colours (2^1), 8 bits = 256 colours (2^8)

Question 19

How do you calculate IMAGE FILE SIZE?

Answer 19

File size (bits) = width X height X colour depth

Question 20

What is a BITMAP image?

Answer 20

Organised grid of coloured squares called pixels

When zooming in or enlarging a bitmap image, the pixels are stretched and made into larger blocks

Appear as poor quality when enlarged too much

Question 21

What is a VECTOR image?

Answer 21

Use scalable shapes such as straight lines and curves, using coordinates and geometry to precisely define the parts of the image

It is more efficient than bitmaps at storing large areas of the same colour because it does not need to store every pixel as a bitmap does

Vector graphics can be scaled without losing resolution

Question 22

What is METADATA?

Answer 22

Data that describes other data

Question 23

Name a LOSSLESS image data compression

Answer 23

PNG

It is often used where the graphic might be changed by another person or where the image contains layers of graphics that need to be kept separate from each other

It is high quality

Question 24

Name a LOSSY image data compression

Answer 24

JPEG

It is often used for digital camera images because it has a fairly small file size for the quality that it displays

Higher compression rate than PNG in the trade-off for quality

Question 25

What is a GIF?

Answer 25

Compresses images to a maximum 8-bit colour depth, making it unsuitable for high-quality photographs

It is often used where transparency is needed on the graphic

GIF can also be used to store simple animated images.

Question 26

What is sound SAMPLING?

Answer 26

Samples of a sound wave are taken at regular intervals

Question 27

What is SAMPLING FREQUENCY?

Answer 27

How often each sample is taken

Question 28

How do you calculate AUDIO FILE SIZE?

Answer 28

File Size (bits) = Sample Frequency X Bit Depth X Recording Length (seconds)

Question 29

Order of units

Answer 29

1 Byte = 8 bits
1 Kilobyte = 1024 Bytes
1 Megabyte = 1024 Kilobytes
1 Gigabyte = 1024 Megabytes
1 Terabyte = 1024 Gigabytes

Question 30

Advantages of compression

Answer 30

• Less internet/ bandwidth is used when files are downloaded/ uploaded
• Transfer speed is quicker
• Less storage space is needed
• Smaller files reduce congestion on the internet
• Audio and video files can be streamed

Question 31

When would you use LOSSLESS compression?

Answer 31

• Text files
• Graphic files with low colour depth

e.g. GIF and PNG image files, compressed text files

Question 32

When would you use LOSSY compression?

Answer 32

• Image files
• Digital sound recordings

e.g. MP3 audio files, PG image files

Question 33

How does RLE work?

Answer 33

Run Length Encoding

Reduces file size by checking for redundancy

e.g. aaaaaabbbbcccdddde = 6a4b3c4d1e

Question 34

What are the encryption protocols?

Answer 34

Data is encrypted using the HTTPS protocol (Hypertext Transfer Protocol - HTTP) with the Secure Socket Layer (SSL)/ Transport Layer (TLS)

Question 35

What is unstructured data?

Answer 35

Data that is stored without being ordered into categories

Difficult to be linked or searched

e.g. images and uploads to social network sites

Question 36

What is structured data?

Answer 36

Stored and organised in an ordered way so that it can be retrieved quickly when it is being searched or queried

Links can be made to create information

Question 37

What is a database?

Answer 37

A persistent and organised store of data

Computers are ideal for storing and manipulating databases as they can search and sort the data faster than a human can