Unit 2: Data Representation

Question 1

What Units is data measured in?

Answer 1

Bit (b) - Single Binary Digit (1 or 0)
Nibble - 4 Bits
Byte (B) - 8 Bits
Kilobyte (kB) - 1000 Bytes
Megabyte (MB) - 1000 Kilobytes
Gigabyte (GB) - 1000 Megabytes
Terabyte (TB) - 1000 Gigabytes
Petabyte (PB) - 1000 Terabytes

Question 2

Why do we use binary format to represent information on a computer?

Common Exam Question

Answer 2

In the exam, you may get asked to explain why we use a binary format to represent information on a computer. The answer is that computers use on and off signals, binary has two states 0 and 1, the binary 0 and 1 state can therefore represent the on and off electrical signals.

Question 3

In our standard number system, we have ten digits (0-9), what is this called?

Answer 3

Denary, Decimal or Base-10

Question 4

Binary, Denary and Hexadecimal Conversions

GoodNotes

Answer 4

All Binary, Denary and Hexadecimal conversions on GoodNotes

GoodNotes

Question 5

What are Character Sets?

Answer 5

Collections of characters that a computer recognises from their binary representations.

Question 6

Why are Character Sets used?

Answer 6

1. Alphanumerical characters are used to make words and strings. They include uppercase, lowercase, digits (0-9) and symbols (? £ @ +)
2. Computers are unable to process these characters directly as they only process binary code so need a way of converting these characters to binary code and vice versa.
3. They can do this using character sets.

Character sets also contain special characters which do certain commands (e.g enter and delete)

Question 7

How are character sets used when you press a button on a keyboard?

Answer 7

Pressing a button on a keyboard sends a binary signal to the computer telling it which key you pressed. The computer then uses the character set to translatethe binary code into a particular character.

Question 8

What does the number of characters in a character set determine?

Answer 8

How many bits you need

Question 9

What is ASCII?

Answer 9

• The most commonly-used character set in the english-speaking world.
• Each ASII character is given a 7-bit binary code meaning it can represent 128 different characters, including letters, numbers, symbols and commands.
• An extra bit (0) is added to the start of the binary code for each ASCII character.
• The codes for numbers, uppercase letters and lowercase letters are ordered letters in alphabetical order with symbols and commands scattered around.

Question 10

What is Unicode?

Answer 10

• Comes in several different forms and tries to cover every possible character or symbol that might be written. Unlike ASCII, unicode uses multiple bytes for each character.
• It covers major langauges, even those with a completely different alphabet.
• First 128 codes is the same as ASCII.

Question 11

What is the formula for the size of a text file?

Answer 11

File size (bits) = number of bits per character x number of characters

Question 12

What is Metadata?

Answer 12

• Metadata is the