Methods of Error Detection (CIE IGCSE Computer Science)

Victoria is entering data into a computer system. The data will be transmitted to cloud storage.

Four 7-bit binary values are transmitted from one computer to another. A parity bit was added to each binary value creating 8-bit binary values. All the binary values have been transmitted correctly.

[5]

Four 7-bit binary values are transmitted from one computer to another. A parity bit was added to each binary value creating 8-bit binary values. All the binary values have been transmitted correctly.

A company selling CDs uses a unique 6-digit identification number for each CD title. The right-most digit (position 1) is a check digit.

For example,

The validity of the number and check digit is calculated as follows:

multiply each digit by its digit position

add up the results of the multiplications

divide the answer by 11

if the remainder is 0, the identification number and check digit are valid.

   valid or not valid? .........................................

   Identification number 2: 8 2 0 1 5 6
   working: ..........................................................
   valid or not valid? .........................................

[3]

Bytes of data transferred using a serial cable are checked for errors at the receiving end using an even parity check.

Can these bytes of data pass the even parity check?