Bootstrapping (was Re: Unix and C)

[Barry Margolin]

In article <403 at bally.Bally.COM> siva at bally.UUCP (Siva Chelliah) writes:
>Q: If you have just the hardware, how would you feed the machine language
>   into the computer ?
>A: I thing you should burn the machine language into a chip, that would 
>   accept a machine language from the user, and execute it. 

Ah, how soon they forget: front panels!

In high school (I graduated 11 years ago) we had a PDP-8 minicomputer,
which contained no bootstrap ROM.  When powering it up, we had to feed in a
short (around ten instructions) program by manually flipping the
front-panel switches.  This program was called the Read-In Mode (RIM)
Loader, and it was a simple loop that read bytes from paper tape reader
into consecutive memory locations, and was used to read a short tape
containing the BIN Loader, which was then run to read in the OS tape.

However, the above answer is correct for most modern computers.  There's
generally a ROM or PROM that contains code that knows how to talk to the
console and read the OS from a disk, and often also contains diagnostics
that can be run without the OS (for instance, to tell you why it's having
trouble talking to the disk).

I've redirected followups to comp.misc, as this no longer has anything to
do with C.
--
Barry Margolin, Thinking Machines Corp.

barmar at think.com
{uunet,harvard}!think!barmar