what is ROM?

10:34 AM in computer hardware

ROM is an acronym for Read-
Only Memory. It refers to
computer memory chips
containing permanent or semi-
permanent data. Unlike RAM,
ROM is non-volatile; even after you turn off your computer,
the contents of ROM will
remain. Almost every computer
comes with a small amount of
ROM containing the boot
firmware. This consists of a
few kilobytes of code that tell
the computer what to do when it starts up, e.g.,
running hardware diagnostics
and loading the operating
system into RAM. On a PC, the
boot firmware is called the
BIOS. Originally, ROM was actually
read-only. To update the
programs in ROM, you had to
remove and physically replace
your ROM chips.
Contemporary versions of ROM allow some limited
rewriting, so you can usually
upgrade firmware such as the
BIOS by using installation
software. Rewritable ROM
chips include PROMs (programmable read-only
memory), EPROMs (erasable
read-only memory), EEPROMs
(electrically erasable
programmable read-only
memory), and a common variation of EEPROMs called
flash memory. This is document ahua in
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