3.2 - Bits, Bytes, Binary Flashcards
What are the prefixes for bytes in order?
Kilo (kB) - 1,000
Mega (MB) - 1,000,000
Giga (GB) - 1,000,000,000
Tera (TB) - 1,000,000,000,000
What were the new prefixes invented in 1988 to avoid confusion with older incorrect prefixes?
Kibi (KiB) - 2^10 = 1024
Mebi (MiB) - 2^20 = 1,048,576
Gibi (GiB) - 2^30 = 1,073,741,824
Tebi (TiB) - 2^40 = 1,099,511,627,776
How many bits was ACSII?
7 bit character set
2^7 = 128
How many bits is Unicode?
16 / 32 bits
What are 4 reasons for transmission errors?
- electrical interference
- power surges
- synchronisation problems
- wear and tear on the cables or connectors
What techniques are there to detects errors in transmission?
- parity bits
- majority voting
- check digits
- check sum
How are parity bits used?
One bit is used as a ‘parity bit’
This is set to either a 1 or 0 to make the number of 1’s and 0’s even or odd
When data is transmitted the parity bit is set at the transmitting end and checked at the receiving end
What is majority voting?
If a bit is flipped erroneously, the receiver computer uses the majority rule and assumes the 2 bits that haven’t changed are correct
What is check digit?
An additional digit at the end of a string of other numbers designed to check for mistakes in input or transmission
The digit is calculated with the modulo 10 system
How does the modulo 10 system work for products with ISBN’s?
Multiply the ISBN with the weight
Add the numbers from the multiplication
Find the remainder of this divided by 10
Then minus this from 10 and this number should be the check digit
How do check sums work?
A total sum of all the bytes transmitted is calculated using an algorithm
This is often sent with the data
The receiving computer calculates the same thing and compares the number to see if they’re the same or there has been a error in transmission
Used for credit cards
What are ASCII and Unicode?
Character sets
What are ASCII and Unicode?
Character sets
