1.1 Data representation

Question 1

What is binary?

Answer 1

A base 2 number system where all numbers and data are represented by using 0’s and 1’s

Question 2

What are the advantages of using binary? (4)

Answer 2

• transmitted easily and reliable
• can be stored and read very easily
• Computers use circuits that can only be on or off (they only have 2 states), so they work well with binary calculations
• the input voltage into computers is not very stable (decreases as the battery decreases), only a system with no voltage would be reliable

Question 3

What is a bit?

Answer 3

An individual 1 or 0

Question 4

What is a byte?

Answer 4

Each group of 8 bits

Question 5

What is a nibble?

Answer 5

4 bits, or half a Byte

Question 6

What is Hexadecimal?

Answer 6

a Base 16 number system that increases in powers of 16

Question 7

What is the denary value for FB3 (hex)?

Answer 7

4019

Question 8

What are the advantages of Hexadecimal? (2)

Answer 8

• Large numbers can be represented in a smaller number of digits (more accurate readings by humans)
• humans can work in hexadecimal when working with binary

Question 9

Every _ binary digits is equal to one hexadecimal digit

Answer 9

4

Question 10

Steps to change from binary to hex? (3)

Answer 10

• split the binary into nibbles
• find the denary value for each nibble
• convert denary value into the corresponding hex digit

Question 11

What are the uses of hexadecimal? (2)

Answer 11

• colours in HTML and CSS
• Media Access Control address (MAC address) - a unique identifier assigned to a network interface controller (NIC)

Question 12

What is machine code?

Answer 12

Instructions that are executed by the CPU, but they’re in binary

Question 13

What is assembly language?

Answer 13

Instructions that are executed by the CPU, but they’re written in words and numbers (e.g. python)

Question 14

What is the difference between machine code and assembly language?

Answer 14

Machine code is in binary and assembly language is written with words and numbers

Question 15

What is the difference between a kilobyte and a kibibyte?

Answer 15

A kilobyte is 10^3 bytes (1000) and a kibibyte is 2^10 bytes (1024)

Question 16

To what power are binary prefixes and decimal prefixes?

Answer 16

Binary - powers of 2
Decimal - powers of 10

Question 17

In one’s compliment, what do the values in the sign column mean?

Answer 17

0 - positive
1 - negative

Question 18

How is the one’s complement used?

Answer 18

All the binary digits are flipped to form the negative equivalent of a number

Question 19

What is the most significant bit in two’s complement?

Answer 19

The leftmost bit

Question 20

How is the two’s complement used?

Answer 20

• all the binary digits are flipped
• then one is added

Question 21

What is an overflow error? (2)

Answer 21

• When a bit has been carried into the position that has a negative place value (e.g. both numbers are positive but the place value is a 1)
• can also happen when the correct result cannot be stored in 8 bits

Question 22

When can overflow error happen? (2)

Answer 22

• adding 2 positive numbers produces a 1 as the most significant bit
• adding 2 negative numbers produces a 0 as the most significant bit

Question 23

What is BCD (Binary Coded Decimal)?

Answer 23

A form of binary representation where each denary digit is converted individually into binary

Question 24

What are the advantages of BCD? (3)

Answer 24

• easier for humans to read large binary than if the number is in pure binary
• Simple to create hardware that only counts in decimal and uses basic calculation (e.g. digital clocks, simple calculators)
• BCD removes problems of floating point rounding errors, making it useful for handling financial transactions

Question 25

How is data stored in financial systems?

Answer 25

• some fractions cannot be stored accurately using binary, due to the fraction not fitting perfectly within a base 2 binary system
• This results in a floating point rounding error
• In financial systems, rounding errors are not acceptable do BCD is used

Question 26

What does ASCII stand for?

Answer 26

American Standard Code for Information Interchange

Question 27

What are the advantages of using ASCII? (2)

Answer 27

• Easy to read, write and understand as it is simple for humans to memorise each character
• smaller storage and transmission size (7 bits for standard ASCII and 8 for extended)

Question 28

What is the disadvantages of using ASCII?

Answer 28

Only works for english

Question 29

What is extended ASCII?

Answer 29

It is ASCII but it includes french and german letters and accents so it is extended to 8 bits and allows a total of 256 characters

Question 30

What are the advantages of using extended ASCII?

Answer 30

Allowed to use more European language characters and accents

Question 31

What are the disadvantages of using extended ASCII? (2)

Answer 31

• 1 bit longer than ASCII so it requires more storage
• cant support easter alphabets

Question 32

What is unicode?

Answer 32

a system with a much larger number of available characters

Question 33

What are the advantages of using Unicode?

Answer 33

Millions of different characters are available due to the large number of bits per character (16 or 32 bits)

Question 34

What are the disadvantages of using Unicode?

Answer 34

2 or 4 times more storage space taken up per letter

Question 35

What are the steps of converting text into ASCII? (2)

Answer 35

• take each letter and find the corresponding decimal value
• change the decimal values into binary