> What is the purpose of EEPROM?

Electrically Erasable Programmable Read-Only Memory is used to store
programming in a piece of a computer's memory - much the same as it is
stored in the BIOS (Basic Input/Output System) chip.

The difference is that the EEPROM chip can be re-programmed, whereas the
older, one-time, PROM chips are permanently programmed.  This is why the
newer EEPROM BIOS chips can be updated.

If the BIOS tells the CPU to go to an address in memory, instead of reading
the A: or C: drive, you can have a computer that boots (very quickly, as it
is already stored in memory on the EEPROM) to the EEPROM.  The programming
on the EEPROM could be like the BASIC that came up on the old PC if it
could not read the A: drive.  Some "rough service" systems used this
technique to boot DOS-on-a-chip, and thus avoid the mechanical frailties
of floppy and hard drives.  I even recall a story that the CIA used
this technique - if your computer doesn't have a floppy drive, it makes
it pretty hard to steal data by sneaking out a floppy disk!

I have read that this is a common way of booting the Windows CE Operating
System on dedicated computers like data logging systems, digital
oscilloscopes, or industrial controllers.

Boyd Ramsay

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