information coding systems
Cards (11)
- Character SetA complete set of all the characters
- Different languages are represented using different character sets
- Character sets are unique to meet global standards
- ASCIIAmerican Standard Code for Information Interchange
- ASCII
- Uses 7 bits to represent 128 characters
- Includes uppercase & lowercase letters, digits, punctuation, special characters, control characters
- 8 bits used to store each character (8th bit sometimes used as parity bit)
- Each character is assigned a denary character code, which is represented and stored in binary
- For English only
- Extended ASCII
- Uses the first 128 ASCII characters, plus additional 128 to form 256 bits
- Characters used in European languages are also included
- Unicode
- 32 bit system
- Uses 8-32 bits for each character
- First 128 characters are the same as ASCII
- Unicode occupies more memory space, due to higher number of bits
- Parity bit
- Number of 1s in each binary code are counted before to check if its even or odd
- Even parity: value of the parity bit is chosen so as to make the total number of 1s in the transmitted data even
- Odd parity: chosen to make the total number of 1s odd
- When data is received, it is checked to see if it is correct
- If number of bits is changed during transmission, error is not detected
- Majority Voting
- Produces data several times and checks if they are the same
- Most commonly occurring value is taken to be correct
- Volume of data being transmitted is increased with the repetition of bits
- Check Digit

- Single digit at the end of binary data added to check it is accurate
- Add digits of numbers together and keep doing so til you get a single digit
- Add digit to end
- However, if values swap position this will go unnoticed
- Modulo 11
- Write out initial number and going from R to L, number them in ascending order starting at 2
- Multiply by their number, and add all values together
- Divide by 11 and subtract the remainder from 11