2.3.1 Data Storage & Compression (B01)

Question 1

bit (b)

Answer 1

(short for binary digit) is the smallest unit of data in a computer. A bit has a single binary value, either 0 or 1.

Question 2

byte (B)

Answer 2

8 bits

Question 3

nibble

Answer 3

4 bits / half a byte

Question 4

bit rate

Answer 4

number of bits transmitted (usually per second)

Question 5

kibibyte

Answer 5

2^10 bytes (1024)

Question 6

the hierarchy of bytes

Answer 6

kibi, mebi, gibi, tebi

(kennard, miss jones, gib, truck)

Question 7

Answer 7

Question 8

Answer 8

Question 9

Answer 9

Question 10

A typical book has about 459 000 characters. Your eReader has half a mebibyte of space left on it. Will a typical book fit in the remaining space? Assume 1 character = 1 byte

Answer 10

459 000 chars = 459 000 bytes
1 MiB =1024 ×1024 bytes
459 000 chars = (459 000)/(1024 × 1024) mebibytes
This is approx. 0.438 MiB, so the book will fit.

Question 11

compression

Answer 11

reducing large file sizes by repackaging/removing some data

Question 12

lossy compression (what, how effective, examples)

Answer 12

permanently deletes data
- can reduce up to 90%
- but can never be reconstructed to its original state

for audio files this is removing frequencies outside out of human hearing range

eg JPEG (images), MP3 (sound)

Question 13

lossless compression (what, how effective, examples)

Answer 13

retains the exact meaning of the original data
done by identifying and removing redundant data (eg if words are used more than once, a lookup table is created and they are converted to tokens pointing to their place in the table)
- can reduce by around 50%
- means file can be reconstructed to original state when decompressed

eg PNG (images), FLAC (audio). ZIP (archiving)