unit 1: data representation

Question 1

16=2^4

Answer 1

four binary digits are equivalent to each hexadecimal digit

Question 2

binary to hexadecimal

Answer 2

split no. into groups of 4 bits
take each group of 4 bits and convert it into equivalent hexadecimal digit

Question 3

hexadecimal to denary

Answer 3

multiply each hex digit by its heading value

Question 4

denary to hexadecimal

Answer 4

successive division by 16 until the value 0 is reached
(16. 32. 48. 64. 80. 96. 112. 128. 144. 160)

Question 5

uses of the hexadecimal system

Answer 5

1. error codes
2. MAC addresses
3. IPv6 addresses
4. HTML colour codes

Question 5

error codes

Answer 5

hexadecimal values refer to memory location of error
automatically generated by computer

Question 6

MAC addresses

Answer 6

refers to no. which uniquely identifies a device on a network
refers to network interface card (NIC) which is a part of device
usually made of 48 bits (64 bits exist) which are shown in groups of two

Question 7

MAC address components

Answer 7

1. first half: identity no. of manufacturer
2. second half: serial no.

Question 8

IP addresses

Answer 8

gives unique address to each device connected to a network

Question 9

diff. between IPv4 and IPv6

Answer 9

IPv4:
* 32-bit no.
*denary / hexadecimal
* decimal point (.)
IPv6:
* 128-bit no.
*broken down into 16- bit chunks
*hexadecimal
*colon (:)

Question 10

HTML colour codes

Answer 10

represents colours of text on computer
intensity determined by hexa value

Question 11

logical binary shifts

Answer 11

shift left = multiplying binary no. by 2

shift right= dividing binary no. by 2

Question 12

left most bit

Answer 12

MOST SIGNIFICANT BIT

Question 13

right most bit

Answer 13

LEAST SIGNIFICANT BIT

Question 14

when does error show in logical binary shift?

Answer 14

when we have exceeded the maximum no. of left shifts possible using a certain register

Question 15

two’s complement : method

Answer 15

1. write no. as + binary value
2. invert each binary value
3. add 1 to that no.

Question 16

ASCII code system

Answer 16

(AMERICAN STANDARD CODE FOR INFO INTERCHANGE)
used in communication and computer systems

Question 17

ASCII ranges

Answer 17

a-z : 097 - 122
A- Z : 065 - 090
0-9 : 048 - 057

Question 18

why Unicode was created?

Answer 18

ASCII doesn’t represent characters in non- western languages
unicode represents all languages

Question 19

sampling

Answer 19

amplitude of analogue sound wave recorded at regular/set intervals

Question 20

sampling resolution

Answer 20

no. of bits used to represent sound amplitude in digital sound recording

Question 21

sampling rate

Answer 21

no. of sound samples taken per sec

Question 22

increasing no. of possible values used to represent sound amplitude…

Answer 22

…increases the accuracy of the sampled sound

Question 23

benefits of using a larger sampling resolution

Answer 23

1. larger dynamic range
2. better sound quality
3. less sound distortion

Question 24

drawbacks of using a larger sampling resolution

Answer 24

1. produces larger file size
2. takes longer to transmit/ download music files
3. requires greater processing power

Question 25

sampling resolution and sampling rate of CDs

Answer 25

sampling resolution = 16 bit

sampling rate = 44.1 kHz

Question 26

meaning of larger dynamic range

Answer 26

diff. between quieter and louder soudns
large gap= quieter won’t be heard

Question 27

image resolution

Answer 27

no. of pixels that make up an image

Question 28

order of memory sizes

Answer 28

{ KB, MB, GB, TB, PB, EB }

Question 29

Formula for image file size

Answer 29

image resolution (in pixels) x colour depth (in bits)

Question 30

formula for sound file size

Answer 30

sample rate (in Hz) x sampling resolution (in bits) x length of sample (in seconds) x [for stereo: no. of channels]

Question 31

lossy

Answer 31

parts of original file cannot be recovered during decompression process

Question 32

lossless

Answer 32

allows original file to be fully restored during decompression process

Question 33

MP3

Answer 33

used for playing music
reduces size by about 90%
* algorithm removes sounds ear can’t hear:
1. outside ear range
2. perpetual music shaping: if 2 sounds played at same time, only louder one can be heard

Question 34

MP4

Answer 34

allows storage of multimedia files
retains acceptable quality

Question 35

JPEG

Answer 35

used for bitmap images
human eyes detect diff. in image brightness better than colour shades
image split into 8 x 8 pixel blocks

Question 36

run length encoding (RLE)

Answer 36

lossless file compression technique used to reduce size of text and photo files