 Error-detection and correction schemes can be either systematic or non-systematic.In a systematic scheme, the transmitter sends the original data, and attaches a fixed number of "check bits" (or "parity data"), which are derived from the data bits by some deterministic algorithm.If only error detection is required, a receiver can simply apply the same algorithm to the received data bits and compare its output with the received check bits; if the values do not match, an error has occurred at some point during the transmission.