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Section A:
General Introduction
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•
Warm Start
•
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A.5.2. The Warm Start
The
computer is up and running.
We see the ready prompt on the
screen
and could start working. This is correct, but for completion, let us put
a few words on the operating system warm start right here.
As already mentioned, the ready prompt is the --sign of life of a specific
operating
system part.
This part of EOS is called "SHF.LL",
because it
represents
in some way the outer
11
shell
11
of the operating
system.
One
part
of an operating system is embedded into the other,
just like
the
shells
of
an onion.
The task of SHELL is to be at
your
service
and
convert your input into meaningful actions.
After a program has been loaded, the presence of SHELL is no longer nec-
essary,
it
is
even undesirable in order to free up memory
space
for
other programs. Hence, it is usual that programs simply ignore SHELL and
overwrite it.
After they have finished,
they call upon the part of EOS
which
has remained in memory (and cannot be renounced) to re-load SHELL
from
drive P:
(the RAM disk) and pass control to
it.
Therefore,
the
usual SHELL prompt re-appears on the screen after each ordinary
program
termination.
This kind of re-loading is called "warm start
11
or "warm boot".
As SHELL
is a relatively small program,
this is done within a moment. Should you
insist on having your system crash,
just erase the file "SHELL.SYS"
on
drive P:.
However, the file is protected against such foolish things by
having
the
file
attributes SYSTEM and R/0 set.
For details
on
file
attributes, please refer to the chapter on filenames.
EOS User's manual
Daeumling & Zimmermann
Page 16
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