New system released

[Moon at MIT-AI (David A. Moon)]

System 50.9 and microcode 701 work well enough to be released to users.  These
are installed on one or two machines and will migrate to more soon.  There are
some minor incompatible changes; the remainder of this message describes the
changes.  Note that using system 50 with a microcode older than 701 will not
work optimally.  Using an older system with microcode 701 will work very poorly.

System 50 requires UCADR 701 or later.  When using the CC debugging program to look
at a machine running system 50, CC should be running in system 50 (or else
load the latest LCADR;QF) or the virtual memory will not work properly and
the machine being debugged will be trashed.

The control-top-letter and meta-top-letter editor commands now work reasonably
on "Space Cadet" keyboards.  For instance, the command to show you the arguments
to the function, a call to which is around point, is control-top-A on the old
keyboards and control-shift-A (the same finger motion) on the new keyboards.

Certain tables are now dynamically allocated, allowing the system to work
with more than 256K of memory.  Also machines with small amounts of memory
will have a few additional available memory pages.

There is a new DEFMACRO keyword, &BODY.  This is like &REST but causes
the editor and grinder to indent the following forms as a "body", i.e. 2
spaces in from the open parenthesis that starts the "call" to the macro.

The "C" command in DIRED is implemented and does the same thing as in
Emacs (source comparison); Meta-X Source Compare and Meta-X Source Compare
Merge are available in Zmacs.

A new function, VALUES, has been installed in the global package; if you
are using this name, you may have a name conflict.  VALUES is a function
of any number of arguments, which returns many values: one for each argument.
You can use this to return multiple values from a function, without using
a PROG anywhere.

The functions in the TIME package have all been renamed, and all their
arguments and returned values have been changed.  In particular, the
WHAT-DATE function has been removed from the TIME package; some people
may use this in init files; you can now use TIME:PRINT-CURRENT-TIME,
which is the same but doesn't print a newline.  Since the time functions
had not been documented anyway, probably nobody is otherwise affected by
this.   The time parser has been greatly spiffed up; if Zmail asks you
for a time, you can now answer in nearly any format that makes sense to
anybody.

The :BLINKER-FUNCTION window initialization keyword has been renamed to
:BLINKER-FLAVOR (for a long time it has been a flavor name rather than a
function name).

The previously announced changes to PUTPROP have been installed; PUTPROP
no longer changes the order of properties in the property list.

All (well, almost all) mouse-sensitive screen areas are now indicated by
outlining rather than inverse video.  This is intended to move toward a
more consistent convention for use of the mouse.

The system now automatically deletes all files on your directory when you
log in.  This is here to encourage users to read these messages, rather than
come and complain to us that they weren't informed of changes.

The special form ZWEI:OPEN-FILE is gone, having been replaced by WITH-OPEN-FILE.
The syntax is essentially the same.  Some users are probably using ZWEI:OPEN-FILE
and will need to switch.

Redefining a traced function no longer automatically untraces it.

BEGF and ENDF are gone; they haven't done anything for two years but may
still exist in some source files.

%HALT is no longer global since it is an internal sub-primitive.
The following symbols are global for the stepper program (they should
have been all along; this was an oversight):  STEP-FORM STEP-VALUE STEP-VALUES

Y-OR-N-P and YES-OR-NO-P no longer accept their arguments in either order.