lossy/lossless data compression

Question 1

what does compression do

Answer 1

•reduces the number of bits in a file
•makes the storage capacity of the file lower
•makes data transfer of the file quicker

Question 2

why is compression good

Answer 2

more data can be stored on a storage device, and transferred in a smaller amount of time.

Question 3

what happens in lossy compression?
(3 things)

Answer 3

•some of the data is lost and can’t be recovered
•greatly reduces file size
•reduces quality of image/sound

Question 4

what is lossy compression suitable for?

Answer 4

images, sound and video

Question 5

what can lossy compression not be used for

Answer 5

text and executable files

Question 6

what happens in lossless compression

Answer 6

•no data is lost, it’s just encoded differently
•can be turned back into original formal

Question 7

what is lossless compression used for

Answer 7

all types of data

Question 8

which is more effective lossy or lossless

Answer 8

lossy

Question 9

what is lossless compression most useful for

Answer 9

documents and executable files

Question 10

what does the CPU consist of

Answer 10

ALU, CU, cache, clock, bus

Question 11

what does the arithmetic logic unit do

Answer 11

performs calculations and logical decisions

Question 12

what does the control unit do

Answer 12

sends signals to control how data moves around the CPU

Question 13

what does the cache do

Answer 13

provides fast access to frequently used instructions and data

Question 14

what does the clock do

Answer 14

the electronic unit that synchronises related components by generating pulses at a constant rate

Question 15

what is a bus and what does it do

Answer 15

collection of wires through which data needs to be written to or read from

Question 16

what does the adress bus do

Answer 16

unidirectional- carries the addresses which data needs to be written to or read from

Question 17

what does the data bus do

Answer 17

bidirectional- carries the actual data or instructions

Question 18

what does the control bus do

Answer 18

bidirectional- carries command and control signals telling components when they should be receiving reads or writes etc.

Question 19

what are registers

Answer 19

tiny, super fast pieces of onboard memory inside the CPU each with a very specific function

Question 20

what do program counters do

Answer 20

hold the address of the next instruction to be executed

Question 21

what does the MAR (memory address register) do

Answer 21

holds the address in memory which data or an instruction needs to be read from or written to.

Question 22

what does the MDR (memory data register) do

Answer 22

holds either data or instruction which has been fetched from memory or is about to be written back from memory

Question 23

what is the accumulator

Answer 23

a set of general purposes registers

Question 24

what happens in the fetch of the FDE

Answer 24

-fetches the next instructions from main memory (RAM)
-brings instruction back into the CPU

Question 25

what happens in the decode of FDE

Answer 25

-inspects the instruction and works out what it is that needs doing

Question 26

what happens in the execute of FDE

Answer 26

-carries out the instruction
-could be: going back to main memory to grab more data, performing a calculation, storing information back into main memory