Units Flashcards
Computers use 1s and 0s for what?
- to represent the flow of electricity
- 1 is sued to show that electricity is flowing
- 0 shows that it’s not flowing
What is a bit (b)?
A single binary digit (1 or 0)
What is a nibble?
4 bits
What is a byte (B)?
- 8 bits
- enough to store one character
What is a kilobyte (kB)?
- 1000 bytes
- most files (e.g. songs, pictures and documents) are measured in kB or MB
What is a megabyte (MB)?
- 1000 kilobytes
- most files (e.g. songs, pictures and documents) are measured in kB or MB
What is a gigabyte (GB)?
- 1000 megabytes
- high definition videos and complex applications are often measured in gigabytes
What is a terabyte (TB)?
- 1000 gigabytes
What is a petabyte (PB)?
- 1000 terabytes
Secondary storage capacity is normally measured in what?
gigabytes or terabytes
If each bit can take two values how man values can a nibble take? How many values can a byte take?
nibble = 4 bits = 2 to the power of 4 == 16 different values byte = 8 bits = 2 to the power of 8 == 256 different values
What are check digits?
- 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.
What is a check digit called in binary data?
A parity bit
What is an even parity bit?
- added to make a binary string have an even number of 1s
What is an odd parity bit?
- added to make a binary string have an odd number of 1s.
What happens if one bit of the binary string is read incorrectly?
The computer will pick up an error. e.g. if an even parity bit is used and 10101101 is read.
What happens if two bits within the same binary string are read incorrectly?
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.
