1 Data Representation

Question 1

convert binary to denary

Answer 1

right to left: each bit is worth 2 times the last bit, add up all the bits with 1’s

Question 2

convert denary to binary

Answer 2

continually divide denary number by 2 until you get to 0, and put 1 as the remainder for odd numbers. To get the binary number, read the remainders from bottom to top

Question 3

convert binary to octal (and vice versa)

Answer 3

for every 3 bits, right to left: each bit is worth 2 times the last bit, add up all the bits with 1’s, for 3 bits is one bit for octal

Question 4

convert binary to hexadecimal (and vice versa)

Answer 4

for every 4 bits, right to left: each bit is worth 2 times the last bit, add up all the bits with 1’s, for 4 bits is one bit for hexadecimal

Question 5

What is hex ABC in octal

Answer 5

ABC=5274

A=1010 B=1011 C=1100 ABC=1010 1011 1100 = 5274
5=101 2=010 7=111 4=100

Question 6

Uses of the hexadecimal system (4)

Answer 6

error codes
MAC (media access control) addresses
IPv6 addresses
HTML colour codes

Question 7

overflow error definition

Answer 7

the result of an equation exceeded the largest possible number which can be stored using a certain number of bits

Question 8

logical shift definition

Answer 8

a logical shift moves binary numbers to the left or the the right. Each shift left is equivalent to multiplying the binary number by 2 and each shift to the right is equivalent to dividing the binary number by 2

Question 9

what is two’s complement

Answer 9

allows binary representation of negative integers
the most important bit (on the far left) of the number becomes a negative
there must be a one in the MIB

Question 10

what is an ASCII code system

Answer 10

American Standard Code for Information Interchange
a character set that consists of 7-bit codes (0-127 in denary)
represents the letters, numbers and characters found on a standard keyboard, together with 32 controd codes

Question 11

sound sampling meaning

Answer 11

measuring the amplitude of the sound wave

Question 12

sampling rate meaning

Answer 12

the number of samples taken in 1 second or the frequency of sound samples taken
measured in hertz (Hz)

Question 13

sampling resolution meaning

Answer 13

the number of bits per sample
also known as the bit depth

Question 14

pixels meaning

Answer 14

the smallest element of a bitmap image

Question 15

colour depth meaning

Answer 15

the number of bits used to represent each colour for each pixel

Question 16

image resolution meaning

Answer 16

the number of pixels that make up an image
for example an image could contain 4096 x 3072

Question 17

bit meaning

Answer 17

the basic unit of all computing memory storage terms
the word comes from (B)inary dig(IT)
the smallest unit of memory in a computer

Question 18

what is one byte in bits

Answer 18

8 bits

Question 19

order of memory size in denary system

Answer 19

1 bit
1 Byte
1 kilobyte
1 megabyte
1 gigabyte
1 terabyte
1 petabyte
1 exabyte

Question 20

order of memory size in binary system

Answer 20

1 bit
1 Byte
1 kibibyte
1 mebibyte
1 gibibyte
1 tebibyte
1 pebibyte
1 exbibyte

Question 21

file size of an image formula

Answer 21

file size = image resolution (in pixels) x colour depth (in bits)

Question 22

file size of a mono sound file formula

Answer 22

file size = sample rate (in Hz) x sample resolution (in bits) x length of sample (in seconds)

Question 23

bandwidth meaning

Answer 23

the maximum rate of transfer of data across a network

Question 24

reasons to reduce/compress files

Answer 24

to save storage space on hard disk drives/solid state drive
to reduce the time taken to stream a music or video file
to reduce the time taken to upload, download or transfer a file across a network (reduces bandwidth)
to reduce costs. for example, when using cloud storage, the cost is based on the size of the files stored

Question 25

what is lossy file compression

Answer 25

the file compression algorithm eliminates unnecessary data from the file
this means the original file cannot be reconstructed once it has been compressed
results in some loss of detail when compared to the original file

Question 26

what might lossy file compression do to an image

Answer 26

reduce the resolution
reduce the colour depth

Question 27

what might lossy file compression do to a sound file

Answer 27

reduce the sampling rate
reduce the resolution
removal of sounds outside the human ear range
if two sounds are played at the same time, only the louder one can be heard by the ear, so the softer sound is eliminated. this is called perceptual music shaping

Question 28

examples of lossy file compression algorithms

Answer 28

MPEG-3 (MP3)
MPEG-4 (MP4)
JPEG

Question 29

what is lossless file compression

Answer 29

with this technique, all the data from the original uncompressed file can be reconstructed
none of the original detail from the file is lost

Question 30

what is RLE

Answer 30

run length encoding
it is a form of lossless/reversible file compression
reduces the size of a string of adjacent, identical data
a repeated string is encoded into two values:
-the first value represents the number of identical data items in the run
-the second value represents the code of the data item