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The Last Word 3.0 Reference Manual
8-54
assuming there were at least four free banks on the target machine – LW would
allocate one bank for the macro/paste/directory buffer (which it always does when
using extended memory, before allocating any other banks as text buffers), three
banks for extra text buffers, and it would enlarge the main text buffer to 19K.
The RESERVE instruction is intended to allocate banks of extended memory for use
by machine code extensions. It’s envisaged that in the future, applications such as
proofreaders and table of contents generators will be written as extensions for LW.
The extensions load at $3300 and must first have space allocated for them with the
EXTPAGES statement, which merely allocates the specified number of 256 byte
memory blocks (to a maximum of 12) above $3300 to house the executable code of
extension programs (this memory is taken from the 19K main text buffer: extensions
are only available when LW is using BANKED memory).
EXTPAGES 4
RESERVE 1
The above statements in LW.SYS will reserve four pages of RAM from main memory
at $3300 for extension code, and a single bank of extended RAM for use by
extensions which require it. If there is insufficient extended memory, or if LW is not
using banked memory, these instructions will have no effect.
Another example:
BANKED ON
BANKS 1,2,3,4,5,6
RESERVE 1
EXTPAGES 8
On a 320K machine running DOS 2.5 with a 64K RAMdisk installed, the LW.SYS file
above will configure LW with four extended text buffers, and one bank for the
macro/paste/directory buffers, reserving a single bank (actually the last in the list) for
use by extensions. Since LW is using banked memory, the main text buffer would be
19K. However, the EXTPAGES statement has reserved 8 pages (2K) at $3300 for use
by extension executable code, reducing the size of the main text buffer to 17K.
You can disable banked memory use altogether by including the following line in
LW.SYS:
BANKED OFF
This will cause LW to ignore any BANK, EXTPAGES or RESERVED statements in
LW.SYS. The main (and only) text buffer will be 16K in size and the paste, macro and
directory buffers will each be only 1K long. This is the same configuration LW will
adopt when run on a standard 64K XL/XE machine.
8.3.2 CONFIGURATION USING OTHER DOS PACKAGES
When LW is loaded on a system using an unsupported DOS (anything other than
SpartaDOS X and DOS 2.5 or MyDOS with the standard RAMdisk drivers), it makes
no assumptions about whether the operating system is using extended memory for
RAMdisks or other purposes. Therefore the default behaviour of the program under
these circumstances is NOT to use banked memory. To use banked memory when