Parity memory or Parity RAM (Random Access Memory) uses a parity bit to detect errors. Parity memory is great for detecting errors but offers no way to correct the error once it occurs. Automatic error correction is possible using Error-correcting code memory (ECC) but not parity memory.
RAM parity checking is the storing of a redundant parity bit representing the parity (odd or even) of a small amount of computer data (typically one byte) stored in random-access memory, and the subsequent comparison of the stored and the computed parity to detect whether a data error has occurred.
The parity bit was originally stored in additional individual memory chips; with the introduction of plug-in DIMM, SIMM, etc. modules, they became available in non-parity and parity (with an extra bit per byte, storing 9 bits for every 8 bits of actual data) versions.