EEPROM

These are what have now evolved into our common Flash ROM. Used in most MicroController development, the Lego RCX, with phones and PDAs it has become much cheaper than it was.

It allows you to erase, and rewrite portions of the ROM regularly, as if it were really a Non-Volatile RAM, although it is usually the case that a write is an expensive operation, and it is much faster to write to RAM.

Hardware is now produced to be updated - that is, firmware can be patched.