UUO Area Scheme for Storage Allocation

Description/definitions:
	UUO Areas, or just "areas", are blocks of core which in theory are
infinitely expandable and thus are very useful for dynamic allocation.
Each area requires several variables of information such as its
current actual core address, size, and pointers (since expansion of area
size may involve shifting the entire area to a less restrictive
neighborhood).  These variables require $ARSIZ consecutive words of storage,
and reference to an area is usually made by addressing this Area-info block
or ARBLK.  The address of this block is called an ARBLK pointer, or ARPT.
For example, to use an area called MSGAR, one simply has
MSGAR:	BLOCK $ARSIZ	; "MSGAR" is the ARPT for this area.
Areas can be of two general types, Text and Image.  In the former, the area
is considered to hold ASCII text, and special operations are done to
preserve character counts, byte pointers, etc. whereas in the latter case
the area is simply a block of words.

General Use:
	One can "open", "close", "expand", and write into areas.
Before doing any of these operations, it is necessary to initialize
the core management routines by means of UARINIT (see description).
Thereafter, UAROPN is used for "opening" or creating areas, and
UARCLS for "closing" or flushing them.  During an area's existence,
its size can be altered with UAREXP, and its type changed with
UARTYP.  


UARINIT addr	; addr: -<# of pages avail>,,<first page #>

The word addressed should be a "page AOBJN" that describes
how many pages are available for use, starting at the specified page.
A very common definition, when all core above the program code is free,
is to put these as the very last statements in a program:

ARPAGS:	FFPAG-400,,FFPAG	; Specify pages for core management
	FFPAG==<.+1777>/2000	; Define FFPAG as # of first free page.




	The format of such a table is currently as follows.  References
can be made directly, but should ALWAYS use the symbol, e.g. to find abs
addr of the area in above example, do MOVE A,MSGAR+$ARLOC.  None of the
locations should be written into unless one is familiar with the way
UUO's operate on the table.  $ARLOC, $ARLEN, and $ARTYP should NEVER be
touched.

$ARID:	< # similar to old "area no."??> (may not be used at all)
$ARLOC:	<absolute addr of area in core>
$ARWPT:	<write pointer>
$ARRPT:	<read pointer>
$ARLEN:	<size of area in words>
$ARCHL:	<# chars left to write into> (only used if type is character)
$ARTYP:	<bits defining area type and other suchlike things>

	%ARTMD = Mode is 1 for character, 0 for word.
	%ARTZM = area should be zeroed when opened, and core additions cleared.