WJEC GCSE Computer Science Data representation overview quiz quiz

Electronic components have two stable states that map onto 0 and 1

Binary is faster to calculate than denary

Binary uses fewer digits than hexadecimal

Humans find binary easier to read

4

8

16

1024

$24$

$28$

$26$

$13$

$01100100$

$01100010$

$11001000$

$01010100$

$256$

$128$

$254$

$255$

$42$

$40$

$26$

$52$

It is what the processor actually stores

Each hex digit represents four bits, making binary shorter to write

It can store negative numbers automatically

It uses only the digits 0 and 1

Underflow

Rounding

Overflow

An arithmetic shift

$2$

$4$

$8$

$16$

Change only the leftmost bit to 1

Flip every bit

Flip every bit, then add 1

Add 1 to the positive value

It can store larger positive numbers

Subtraction can be done by addition with a single adder

It uses fewer bits per number

It does not need a sign bit

$68$

$69$

$100$

$67$

To make text files smaller than ASCII

To replace binary storage

To represent characters from many languages, plus symbols and emoji

To remove the need for a character set

$16\,000$ bytes

$2000$ bytes

$250$ bytes

$16\,000$ bits

Reduce both quality and file size

Improve quality but reduce file size

Have no effect on file size

Improve quality but increase file size

Lossless permanently removes data; lossy keeps all data

Lossy permanently removes data; lossless reconstructs the original exactly

Both reconstruct the original exactly

Lossless is always used for photos and music

$4\text{R}\,3\text{G}$

$\text{R}4\,\text{G}3$ with no order

$7$ characters unchanged

$3\text{R}\,4\text{G}$