(ROM
Basic
Input
Output
System) The BIOS in a PC stored on a ROM chip. Early PCs used a ROM BIOS, but PCs today use a flash memory BIOS because it can be updated in place. In order to update a ROM BIOS, the computer case had to be opened, and the ROM chip had to be located and replaced. Nevertheless, a BIOS stored in ROM is more secure than one in flash memory, because it cannot be changed from an external source. See
BIOS and
ROM.