| parity bit
Because old modems transmitted data
one character at a time, each character had to have its own individual
error check. The usual rule was to add an extra bit (the parity bit) at
the end of each character before the stop bit. This bit would be set to 0
or 1 based on the value of the previous data bits. These days, modems
gather data into packets and send a larger 2- or 4-byte error-check value
to validate data in the entire packet. So a parity bit is no longer
necessary. |