data representation

Question 1

Units of Data Storage

Answer 1

o Bit (1 or 0)
o Nibble (4 bits)
o Byte (8 bits)
o Kilobyte (1000B)
o Megabyte (1000KB)
o Gigabyte (1000MB)
o Terabyte (1000GB)
o Petabyte (1000 TB)

Question 2

why Data must be stored in binary

Answer 2

because computers use switches that can be either on or off to process data.

Question 3

what does
0 + 0,
1 + 0,
1 + 1,
1 + 1 + 1 equal to

Answer 3

0, 1, 10, 11

1 + 0 = 1
1 + 1 = 0 (carry the 1 across)
1 + 1 + 1 = 1 (carry the extra 1 across)

Question 4

which direction does the binary shift to multiply / divide

if a number shifts 3 places right or 4 places left what happens to the number

Answer 4

left and right

halves 3 times ( ÷ by 2 to power of 3 = 8)
doubles 4 times ( x by 2 to power of 4 = 16)

Question 5

if a number shifts 3 places right or 4 places left what happens to the number

Answer 5

halves 3 times ( divided by 2 to power of 3 = 8)
doubles 4 times ( multiplied by 2 to power of 4 = 16)

Question 6

what denary number A mean in hexadecimal

Answer 6

10

Question 7

Data Capacity: sound

Answer 7

Sound: File size = Sample rate (Hz) x Duration (s) x Bit depth (bits)

Question 8

data capacity: image

Answer 8

Image: File size = Colour depth x Image height (px) x Image width (px)

Question 9

data capacity: text

Answer 9

Text: File size = Number of characters x Bits per character

Question 10

how does overflows happen

Answer 10

when you get a result that requires more bits than expected

Question 11

Character Set meaning

Answer 11

stores all the characters that the computer can represent using unique binary codes for each.

Question 12

ascii meaning

Answer 12

ASCII – uses 8 bits for each character and represents 256 characters.

Question 13

unicode meaning

Answer 13

Unicode – uses 16 bits for each character and covers every possible character and all major languages.

Question 14

images meaning

Answer 14

 Represented as a series of pixels, represented in binary.
 Each colour is represented by a binary code.
 If a pixel has 3 bits, it can make 23 colours per pixel.

Question 15

Colour Depth meaning

Answer 15

 Number of bits used for each pixel.
 More bits mean that more colours can be represented.
 Improves image quality and increases file size.

Question 16

Resolution meaning

Answer 16

 Number of pixels in the image.
 The higher the resolution, the more pixels the image is made of.
 Improves image quality and increases file size.

Question 17

analogue sound and sound wave meaning

Answer 17

 Analogue sound waves need to be converted into digital form (ADConverter)
 Sound wave is sampled meaning that the amplitude is measured at set intervals.

Question 18

what is each sample stored as and what is the sample rate and what does greater sound rate mean

Answer 18

 Each sample is stored sequentially as a binary number.
Sample Rate:
 Number of samples taken per second (Hz).
 Greater sample rate improves sound quality and increases file size.

Question 19

bit depth meaning and greater bit depth improvement

Answer 19

Bit depth:
 Number of bits available to store each sample e.g. 16 bits.
 Greater bit depth improves sound quality and increases file size.

Question 20

duration meaning

Answer 20

Duration – length of time the sound file lasts.

Question 21

what is compression needed for

Answer 21

Compression is needed to speed up streaming, downloading files, loading web pages, and meeting size restrictions (e.g. email).

Question 22

lossy compression

Answer 22

Lossy Compression:
 Reduces the file size more so it uses less bandwidth to transmit and is faster to upload.
 Removes any unnecessary detail e.g. reducing image quality.
 Suitable for images and videos.
 Data will be permanently lost.

Question 23

lossless compression

Answer 23

Lossless Compression:
 No data is lost/removed (only temporarily compressed meaning files can be decompressed).
 Suitable for text files as they require all data to be kept in order to remain accurate