Data representation

Question 1

What is a natural number?

Answer 1

positive integer

Question 2

What is a real number

Answer 2

Any number that’s real

Question 3

What is a rational number

Answer 3

any number that can be represented with a fraction

Question 4

What is an irrational number

Answer 4

Any number that can’t be represented with a fraction

Question 5

How do you convert from denary to hex

Answer 5

0-9 = 0-9
10-15 = A-F

Question 6

What is unsigned binary?

Answer 6

binary that represents exclusively positive numbers

Question 7

How do you add binary

Answer 7

0 +0 = 0
0+1 = 1
1 +1 = 10
1+1+1 = 11

Question 8

How do you multiply binary

Answer 8

Do the same thing as regular multiplication

Question 9

What is two’s complement and how does it work?

Answer 9

it is a method of working with negative binary values, where the most significant bit is negative.

Question 10

How do you convert denary to binary using twos complement

Answer 10

• Write out the binary version where it is positive.
• starting from the least significant bit write out all the numbers, until you reach the first one (first being the first on the right hand side) .
• Flip all the bits from then on, including the one

Question 11

How do you subtract binary

Answer 11

Change the number you are subtracting, to a negative value, and add the two numbers together

Question 12

How do you represent fixed point binary

Answer 12

all points after the decimal point are 2^-n

Question 13

How do you convert floating point binary to denary.

Answer 13

• calculate the value of the exponent

-Move the binary point in the mantisa by the amount specified by the exponent.

or denary = mantissa * 2^exponent

Question 14

How do you convert denary to floating point binary?

Answer 14

• Calculate the value into fixed point binary
• Normalize the binary by moving the decimal point to between the last 1 and the zero after that.
• Depending on how you moved the point, change the exponent to do the opposite of that.

Question 15

Why use fixed points vs floating point?

Answer 15

Floating point has a much larger range of numbers that can be produced with the same number of bits.

Fixed point can be processed faster as the decimal doesn’t need to be calculated.
The error will always be the same.
better when speed is more important than precision.

Question 16

what is underflow and overflow

Answer 16

Underflow - when a number is too small to be represented with the number of bits allocated

Overflow - When a number is too large to be represented with the number of bits allocated.

Question 17

What is normalization in terms of binary

Answer 17

A process for adjusting numbers onto a common scale.

Question 18

What is absolute error

Answer 18

The actual difference between the value you are trying to reach and the value you have

Question 19

Whats is relative error?

Answer 19

absolute error / number you’re trying to reach

Question 20

What is ascii?

Answer 20

a standard binary coding system for characters and numbers.

Question 21

what is unicode?

Answer 21

a binary coding system that has superseded ascii

Question 22

What is a parity bit and how does it work

Answer 22

a way of checking if data has been successfully transmitted

for even parity, if there is an odd number of 1s, the parity bit( the last bit) is set to one

Question 22

what is majority voting

Answer 22

A method of checking for errors by producing the same data several times and checking for errors.

Question 22

What is colour depth

Answer 22

the number of bits or bytes allocated to represent the colour of a pixel in bitmap.

Question 22

What is the formula for resolution

Answer 22

number of pixels wide * number of pixels long

Question 23

Whats the difference between analogue and digital signals?

Answer 23

analogue data are usually infinitely variable, whereas digital data is usually discrete.

Question 24

How do analogue to digital converters work(microphone)

Answer 24

Sound is inputted in the form of changes in air pressure and converted to electrical signals. Which are then converted into digital signals.

Question 25

How does sound sampling work?

Answer 25

a series of recordings of amplitude taken at a given frequency, are recorded.

Question 26

how do you calculate the size of a digital recording?

Answer 26

sample rate * length of recording * sample resolution

Question 27

What is Nyquists theorem?

Answer 27

to faithfully recreate an analogue signal, the sampling frequency needs to be at least twice the highest frequency that is audible.

Question 28

What is lossless compression

Answer 28

Lossless is no data is lost lossy data is lost.

Question 29

What is Run length encoding?

Answer 29

Where data is repeated, the data is recorded, then the number of times, it is repeated BBB - > 3B

Question 30

What is dictionary based encoding?

Answer 30

Common occurrences are put into a dictionary, where they are then assigned a token which is recorded.

Question 31

What is plaintext?

Answer 31

data in a form humans can read

Question 32

What is ciphertext

Answer 32

Data that has been encrypted

Question 33

What is a vernam cipher

Answer 33

a cipher that uses a one time pad and is xor’d to create ciphertext
mathematically secure

Question 34

What is a transposition cipher

Answer 34

a cipher with data mixed around

Question 35

what is a baudot code?

Answer 35

a five digit character that predates ascii