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Section C:
2) The less-than character
"<".
Utility Programs
****************
*
$DO
*
****************
This
character explicitly declares a line as program
input
line.
Normally,
$DO passes the file contents to the command
interpreter
only.
All
programs
which
require input from the
keyboard
must
further be served manually.
In these cases, lines beginning with a
less-than character will be passed to the program.
Some special regulations are valid now: If a program calls for more
input than program input lines are present in the file, $DO switch-
es
back to the keyboard unt-il the program has tl];!rminated.
On
the
contrary,
if there are more input lines than the program requests,
the
command interpreter displays a warning that superfluous
input
has
been ignored.
It
~hen
resumes processing at the
next
system
command.
3) The question mark.
If
a line begins with a question mark,
an .:input line is
expected
interactively
from the keyboard.
This facility is available
with
both the system mode and the program input mode.
4) The Semicolon.
This character is used to mark a comment;
however, this feature is
available
with system mode only.
Such a line is not permitted
as
program input.
C.l@.4. Execution Protocol
In
order to let you know when $DO is active,
two kinds of
indications
appear. First, the text "Execute" is displayed in the fifth field of the
status line.
Further, the ready prompt of the SHELL program (but not so
with the menu program USRSHELL) is modified.
For each activce $DO
run,
an
additional greater-than character
11
) "
is displayed.
Hence,
with
a
normal $DO run, the prompt looks like:
>>
If another $DO run is executed from within a $DO run, the prompt has the
following format:
>>>
and so on.
EOS User's manual
Daeumling & Zimmermann
Page 75
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