A type of RAM that add ERROR DETECTION AND CORRECTION circuitry to automatically detect and correct a single BIT ERROR in any of the chip. Such errors are often induced, for example, by stray alpha particles emitted from minute amounts of radioactive elements in the chips' packaging.
If fitted at all, error correction schemes for personal computers work by adding a single extra parity BIT to every BYTE (which is why RAM is built from banks of nine rather than eight chips). The memory circuitry calculates the PARITY, odd or even, of the bits in each bank, so any single bit error will be detected and a PARITY ERROR signalled. MAINFRAME and M IN ICOM PUTE R error correction schemes typically add multiple parity bits that allow the exact location of the changed bit to be identified, so that it can be corrected.