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Section B:
Command Input
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*
Command Interpreter
*
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B.l. The Command Interpreter
The first time you insert your EOS system disk into the drive and switch
the
machine on,
you will see a "greater-than
11
character on the
screen
before the computer calms down after the system is loaded and the lights
at the disk drives go out.
This character is the "ready" prompt of EOS.
It
signalizes
that the command interpreter is now expecting a
command
from
you.
For still better clarity,
the text "E 0 S" appears
in
the
leftmost field of the status line.
You may now enter any text you like.
The
interpreter then tries to interpret this as a command.
In the sub-
sequent chapters we are going to discuss how the interpreter works.
One
remark in advance:
When executing commands,
several
">"
characters
in
sequence
appear
according to the nesting level of
$DO.
For
details,
please refer to the description of the $DO program.
B.l.l. The Screen Editor
Before we discuss details of the command interpreter,
the arrow keys on the righthand side of the keyboard.
you
can
move the cursor to any desired place on the
write something nice on the screen if you like.
just press one of
You will see that
screen.
You
may
Of course,
there is a well-thought background with it: When you enter a
command but make a mistake, you are able to correct the mistype with the
aid of the arrow keys.
Two further keys serve for such changes, both of
them located near the _upper right edge of the keyboard. One of them, the
"DEL" key,
erases the character just under the cursor. The other one is
the
"INS" key which has the opposite effect:
it inserts a blank at the
cursor position so you can make room for input corrections.
When you type a whole lot of characters indiscriminatedly,
you will see
that you cannot write at the leftmost screen column.
The reason is that
the
system prompt
">"
appears here,
which has to remain and therefore,
must not be overwritten.
The
"ENTER" key has a special function.
When you
press
"ENTER",
the
whole
story comes to an end.
The command interpreter then accepts
the
line where the cursor is currently positioned, and tries to interpret it
as
a command (disregarding,
of course,
the first character which
you
cannot change anyway) .
EOS User
1
s manual
Oaeumling & Zimmermann
Page 33
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