error checking and character sets Flashcards
what is a parity bit
an extra bit added to a string of binary code to ensure that the total number of 1-bits in the string is even or odd
how to get an even parity
If the data already has an even number of 1-bits, the parity bit is set to 0; if odd, the parity bit is set to 1
how to do an odd parity
Ensures the total number of 1-bits in the data is odd. If the data already has an odd number of 1-bits, the parity bit is set to 0; if even, the parity bit is set to 1
what would happen if one of the bits get corrupted using parity bit
the computer will change one of the bits, however it doesn’t know exactly which but has been corrupted
what is majority voting and wheres it used
an error detection and correction method where each bit of data is sent multiple times (usually three times). The receiver checks each set of bits and uses the value that appears most frequently.
- used in space communication, critical financial transactions
What is a check digit and how is it used?
- an additional digit added to a number (such as a barcode or bank account number) that is calculated from the other digits in the number.
- It is used to detect errors in data entry or transmission.
Where would check digit be used in?
In applications, where therewill be manual input, which has high likelihood of human error
what are checksums
- a mathematical algorithm applied to a block of data
— the data from the block is used in order to create the original checksum which is then added and transmitted along with the original data
— if the checksums match, the data has been transmitted correctly
how many combinations of 0s and 1s can a byte hold
256
how many bits are in a byte
8
what are character sets
a collection of characters used to represent text in a computer system
how to fix there not being enough characters
create a character set that is larger than 1 byte/8 bits
unicode character sets are at least how long
16 bits long, giving us an increase in combination of 0s and 1s
what is the job of the parity bitin odd or even parity
- used to ensure that the total number of 1s in each byte, including the parity bit equals an odd or even number
what is overflow
where a carry from the most significant bit requires an additional bit
what is an unsigned representation
a binary representation that can only represent positive numbers
what is signed representation
can represent both positive and negative numbers
why was unicode introduced instead of ascii
- to enable the representation of a greater range of characters
- so that more languages can be represented
- improved portability of documents
advantages of using majority voting over parity bit
- majority voting can identify and correct errors due to the majority bits being taken as the correct value
- more effective at detecting errors, as parity bit may miss errors if an even number of bits are corrupted
- can detect multiple errors as each triplet represents one bit of data and can identify an error on that bit
explain how the even parity works using the roles of the sending and receiving device
- sender counts the number of 1s in the bit pattern and adds an extra bit to ensure even number of 1s
- receiver counts the number of 1s in the bit pattern received
- if there are an odd number of 1s, it identifies that an error has occurred
A data transmission system uses even parity.
Explain how the receiver will perform error detection on a received byte
- If the number of 1s received/in the byte is even, the data is (assumed to have been)
received correctly - If the number of 1s received/in the byte is odd, the data has been corrupted / is
incorrect;
what is a byte
a group of 8 bits
how many values can be represented with n bits
2^n
quantities of bytes (10^n)
- kilo, k - 103
- mega, M - 106
- giga, G - 109
- tera, T - 1012
