APPLICATION NOTE #186
 REDUCING PRINTER FILE MEMORY REQUIREMENTS IN XYWRITE III PLUS
 Rev. 01



 This application note is intended to give you some tips on how to 
save memory in a printer file even as you add default commands and 
create new PT (Print Type) tables.

 When a printer file is loaded into memory in XyWrite, its data is put 
into one 64K buffer in the computer's working memory (called RAM). 
Since 1K=1024 bytes, the actual number of available bytes is 65,536. 
This buffer is broken down into the following three sections:

 * A bookkeeping section for font, attribute, and width table names.

 * A code section for fonts and attributes.

 * Space for width tables.

 If you exceed the 64K limit, the message "Out of Memory" appears. A 
second memory constraint is mode entries, of which the maximum 
allowable is 750. The message "Too Many Mode Entries" indicates that 
you have gone over that amount.

 The printer files provided with XyWrite are well within these limits. 
However, if you customize your printer file heavily, or if you just 
want to reduce the amount of memory it uses, you can try one or more 
of the memory saving techniques described below.


 COMMENTING OUT
 The size of a printer file on disk is not directly related to its 
size when loaded into memory. To reduce the amount of memory required 
by the printer file while retaining all the information it contains, 
you can "comment out" sections of the file which you don't often use 
by placing a semicolon at the start of each line in the section.

 Note #1 The comment lines in the printer file do not take up any 
space in the memory buffer. Therefore, deleting comment lines does 
not increase the available memory.

 REDUCING THE BOOKKEEPING SECTION
 Another way of reducing the amount of memory the printer file uses is 
to decrease the amount of space in its bookkeeping section. You can 
accomplish this by abbreviating the attribute, font, and width table 
names in the printer file. For example, change COURIER to CO, or 
MED-COURIER to M-C. Each letter deleted reduces the bookkeeping 
section by one byte. Therefore, you save five bytes every time you 
use CO instead of COURIER.


 REDLINING CAPABILITY
 If you have INSERT and DELETE attributes defined in the printer file 
for redlining, you may get the "Too Many Mode Entries" message even 
though you have only defined 250 or so modes in PT tables. That is 
because XyWrite automatically creates redlining modes--INSERT and 
DELETE equivalents--for each mode definition in your printer file. 
Thus, XyWrite actually triples the number of mode statements you add 
to your printer file.

 You can free up memory while retaining the redlining features for a 
limited number of PT tables by changing the names of the INSERT and 
DELETE modes (e.g., to INS and DEL respectively). XyWrite does not 
automatically create redlining modes unless it finds INSERT and 
DELETE attributes specifically named. Follow the procedure outlined 
below:

 1. Call the printer file to the screen.

 2. Shorten the names of the INSERT and DELETE attribute tables to INS
    and DEL.

 3. Add the INS and DEL mode statements to those PT tables for which 
you want
    to retain redlining modes, using the new attribute names you 
selected in
    step 2. For example:

    MD IN+PICA+INS
    MD DN+PICA+DEL
    MD IB+PICA+BOLD+INS
    MD DB+PICA+BOLD+DEL

    See the conversion table for redlining modes in Chapter 5 of the 
XyWrite
    III Plus Reference Guide.

 Note #2 Be sure to add mode statements for all modes in the PT table 
which are to have redlining capability.

 By defining redlining for only specific modes and PT tables, you can 
increase the number of mode entries available to you. Of course, if 
you never use redlining at all, you can remove the INSERT and DELETE 
attribute tables from the printer file entirely, or comment them out
 with semicolons.


 DELETING UNNECESSARY ELEMENTS
 Another way to save on the memory required by a printer file is to 
eliminate any fonts, attributes, or width tables for which you have 
no need. For example, if you never use Helvetica-Bold, you may as 
well delete all the font and width tables that support it.


 Note #3 When deleting tables, it is a good idea to leave one 
semicolon between the tables that remain.

 Caution: Do not delete the Mode Micro line (MD + MM + Micro) that the 
PT tables in your printer file may contain. This line is essential 
for some printers to microjustify properly.

 For each of the fonts and attributes you delete, you must also adjust 
the corresponding PT table. Instead of deleting the entire PT table, 
you should only delete the individual line in each PT table which 
contains that attribute or font (or change that line to access an 
available font/attribute).

 Note #4 Be careful that you do not delete mode normal.

 Width tables in a printer file begin with the letters "WD" and end 
with "ET." Width tables list the width of each character (in width 
units) of each available font for that particular printer file.

 The name of the width table that a font uses is specified after the 
"UW:" in the font table.

 Still another way to conserve memory is to adjust the width tables 
for the fonts you are keeping. Each width table lists a standard 
width, an example of which is shown below:

    SW=90

 If you see that any characters list the standard width as their width 
(for example: /\ijlt=90), you can delete that entire line from the 
width table. Any characters not listed in the width table 
automatically take the standard setting.


 MONITORING MEMORY USAGE
 The only way to determine whether or not you have exceeded the 64K 
buffer or the 750 mode statement limit is to load the printer file 
into memory, and then watch for error messages (i.e., "Out of Memory" 
or "Too Many Mode Entries").

 As you adjust your printer file(s), you can check to see how much 
memory you have saved by pressing Ctrl_M. This brings up the Memory 
Usage screen, on which you can see the amount of memory the printer 
file is using and how much you have left.

 On the Memory Usage screen, next to "Printing" in the "Feature" 
column you will see a value of 17K under the "Program" column. This 
is the space that is required to give XyWrite printer capability, and 
it will not change.

 The K value in the column under "File" is the amount of memory being 
used by the particular printer file that you have loaded. It is here 
that any savings of memory as a result of trimming the size of, or 
commenting out sections from, your printer file(s) will be reflected.

 The total available memory is listed in K at the bottom left of the 
screen.

 It's a good idea to copy the printer file under a different name 
before you begin to customize it to ensure that you will always have 
a fresh copy to look at if anything goes wrong. You should also save 
and load the file several times while you're customizing it. This 
helps you to debug the printer file and determine its memory 
requirements.

 Tip: Using the LP command rather than LOAD when loading a newly 
customized printer file allows any error messages that may appear to 
remain longer on the prompt line.


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