Units

Question 1

Computers use 1s and 0s for what?

Answer 1

• to represent the flow of electricity
• 1 is sued to show that electricity is flowing
• 0 shows that it’s not flowing

Question 2

What is a bit (b)?

Answer 2

A single binary digit (1 or 0)

Question 3

What is a nibble?

Answer 3

4 bits

Question 4

What is a byte (B)?

Answer 4

• 8 bits

- enough to store one character

Question 5

What is a kilobyte (kB)?

Answer 5

• 1000 bytes

- most files (e.g. songs, pictures and documents) are measured in kB or MB

Question 6

What is a megabyte (MB)?

Answer 6

• 1000 kilobytes

- most files (e.g. songs, pictures and documents) are measured in kB or MB

Question 7

What is a gigabyte (GB)?

Answer 7

• 1000 megabytes

- high definition videos and complex applications are often measured in gigabytes

Question 8

What is a terabyte (TB)?

Answer 8

• 1000 gigabytes

Question 9

What is a petabyte (PB)?

Answer 9

• 1000 terabytes

Question 10

Secondary storage capacity is normally measured in what?

Answer 10

gigabytes or terabytes

Question 11

If each bit can take two values how man values can a nibble take? How many values can a byte take?

Answer 11

nibble = 4 bits = 2 to the power of 4 == 16 different values
byte    = 8 bits = 2 to the power of 8 == 256 different values

Question 12

What are check digits?

Answer 12

• a way of checking if data has been entered and read correctly
• they are digits added to the end of numbers (e.g. ISBNs on books) and are calculated using the other digits in the number.
• if the check digit is correct when data is read, then it’s likely the data has been read/entered correctly.

Question 13

What is a check digit called in binary data?

Answer 13

A parity bit

Question 14

What is an even parity bit?

Answer 14

• added to make a binary string have an even number of 1s

Question 15

What is an odd parity bit?

Answer 15

• added to make a binary string have an odd number of 1s.

Question 16

What happens if one bit of the binary string is read incorrectly?

Answer 16

The computer will pick up an error. e.g. if an even parity bit is used and 10101101 is read.

Question 17

What happens if two bits within the same binary string are read incorrectly?

Answer 17

Then no error will be detected. e.g. if an even parity bit is used and the binary string is 10100000 is read as 10000100 then no error will be picked up.