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Alphanso's Assembler Assylum
by SDH
_Generating a UNIVERSAL file for Your MACROs_
Hey gang! How are you and your MACROs these days?
This month let's learn how to generate our own
personal UNIVERSAL file filled with our own MACRO
definitions. Once we have created the MACROs we
need and place them in our special universal file,
each time we write a new assembly language program
we can "assume" that our MACROs are part of the
entire library and use them without ever defining
them within the source code! Slick! If you have
missed the last two sessions of the Assylum, be
sure to catch up on your reading. Talk about
getting fancy!
_Why a Universal File?_
Why would one ever want to create a univeral file
in the first place? A couple of good answers to
this question. One reason is that it will save you
a good deal of time: you only have to define your
favorite MACROs once. Second reason: program
compactness. If you begin to create more and more
custom MACROs, you could have page upon page of
definitions before you even begin the main body of
your program. Third reason: program readability. If
you properly name your MACROs and provide solid
comments within the main body of your code, the
final product will be much more readable. Fourth
reason: speed. Rather than copying in all your
MACRO definitions, you will be able to SEARCH for
these definitions at assembly time - much faster.
Finally, it's cool... very cool. All assembly
language programmers like to "be cool".
_How to Construct a Universal file_
Next step, since we all decided that cool is
"in", is to create a UNIVERSAL file. You will find
that a universal source code file looks very
similar to our previous files. The simple rules to
follow are listed below. Rule 1: you cannot use
any SEARCH lines from within a .UNV source file.
Rule 2: you cannot use the COPY command either (we
haven't discussed this, but COPY will basically
"yank" in a piece of .M68 code upon assembling).
Rule 3: a .UNV source code file may only contain
MACRO definitions and SYMBOL definitions - NO CODE
may be generated. Not as spooky as you think. If
you are real interested in looking at a .UNV file,
LOG to the MAC: account, DSK0:[7,7], and VUE (or
TYPE) SYS.M68 or TRM.M68. Most of the information
in these two files consist of SYMBOL definitions,
but TRM.M68 has at least one MACRO within the file
towards the bottom. Both SYS.M68 and TRM.M68 when
assembled create SYS.UNV and TRM.UNV - two files we
have SEARCHed over and over.
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Now that the rules are clear, the rest is a snap.
Let's once again use the file JOBRUN.M68 as our
example. VUE JOBRUN.M68 from last months session
(or get JOBRUN.M68 off the Network, PPN [100,51]).
Unyank the MACRO portion of the file. You can do
this by following these steps: placing the cursor
at the first DEFINE statement and hit a _|cP|_. Now
move the cursor to the last ENDM statement of the
MACRO definitions and hit another _|cP|_. You have
just "marked" a block of text. Now hit a _|RETURN|_
to move the cursor out of the "dim" block you just
marked. Hit and _|ESC|_ to get to VUE command mode
(the ">") and type U MYMACS (for "unyank MYMACS").
This will create a file called MYMACS.M68. The
cursor will be resting at the ">" at this point.
Now type DELETE. This will delete the block you
marked from within JOBRUN.
We still are not done. Again hit an _|ESC|_ to
return to the text of JOBRUN. Notice that the
MACROs have been removed from this file. In order
for the assembler to "find" our MACRO definitions,
we need to add in another SEARCH instruction (just
below SEARCH TRM). This SEARCH line should read
SEARCH MYMACS. What this instruction line will do
is inform the assembler to SEARCH a file called
MYMACS.UNV (notice the .UNV extension). All a
SEARCH does is locate any MACRO or SYMBOL
definitions within a given .UNV file for
processing. If you never use any of the MACROs
within MYMACS.UNV but still included the SEARCH
instruction, no errors would occur and it would be
"legal beagle". If you do use a MACRO or a SYMBOL
from MYMACS, then the SEARCH statement would
provide the proper definition. Simple!
Finally, we need to create the .UNV file from
MYMACS.M68. Before you assemble JOBRUN, Finish from
VUE and now VUE MYMACS.M68. At the top of the file,
we need to inform the assembler that this .M68 file
will generate a .UNV file. We do this by placing at
the top of the file the following one line opcode:
UNIVERSAL (see enclosed code below). Now assemble
MYMACS.M68. Notice that the assembler only goes
through two phases of assembly, and it also informs
you that the Universal file is finished. Bingo -
instant library!
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_UNIVERSAL_
_ DEFINE TYPEIT V,B_
_;+---_
_;| TYPEIT will process a JCB variable that is two words packed RAD50 data_
_;| and type this variable to the screen in ascii format._
_;| where_
_;| V = variable to be UNPACKED_
_;| B = buffer area to place unpacked characters_
_;+---------------------------------------------------------------------------_
_ LEA A1,V(A4) ;A1 points to variable to be unpacked_
_ LEA A2,B(A5) ;and ^ A2 to byte "0" of "BUFFER"_
_ UNPACK ;get the letters unpacked_
_ UNPACK ; ...for up to full letters_
_ CLRB @A2 ;Place a "null" after the characters_
_ LEA A2,B(A5) ;Repoint A2 to byte "0" of "BUFFER"_
_ TTYL @A2 ;Print out all chars until a null_
_ENDM_
_DEFINE PRTTAB AA,BB_
_;+---_
_;| PRTTAB acts just like "PRINT TAB (#,#) from within BASIC_
_;| where_
_;| AA is the first #, BB is the second #_
_;+------------------------------------------------------------_
_ MOVB #AA,D1 ;move 1st number into D1_
_ LSLW D1,#10 ;shift it left 8. bits_
_ MOVB #BB,D1 ;move in 2nd number_
_ TCRT ;and perform TCRT call_
_ENDM_
_DEFINE TABDWN AA,BB_
_;+---_
_;| TABDWN - or "TAB DOWN" will place the cursor at the row specified by_
_;| AA and the column specified by BB. Assumes a data register_
_;| (AA) has been "dedicated" to keep track of which row._
_;| where_
_;| AA is a dedicated data register holding current row number_
_;| BB is the column number_
_;+----------------------------------------------------------------------_
_ MOVB AA,D1 ;move in value from dedicated reg._
_ LSLW D1,#10 ;shift it left 8. bits_
_ MOVB #BB,D1 ;move in column number_
_ TCRT ;and perform TCRT call_
_ INC AA ;increment dedicated data register_
_ENDM_
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Now we are ready to assemble JOBRUN. Type M68
JOBRUN and watch how the assembler will SEARCH
MYMACS at the appropriate time and generate
JOBRUN.LIT with the exact same hash code total as
before. Wasn't that easy???
Now for some questions and answers. First, where
should you place MYMACS.UNV? Probably the best
location is in the MAC: account, DSK0:[7,7]. That
way, no matter what PPN you are currently in, if
you have a SEARCH MYMACS instruction line in a file
you are creating, the assembler will find this
file. Next question: how come the assembler found
MYMACS during this session when I didn't move
MYMACS down to DSK0:[7,7]? The answer, as you have
probably already guessed, is that the assembler
will look in the PPN you are currently working in
if it cannot find the .UNV file in the MAC:
account. What if I want to add more of my favorite
MACROs to MYMACS? Well, if you leave MYMACS.M68 in
the MAC: account, each time you generate a new
MACRO that you think you will use over and over,
simply VUE MYMACS.M68, add in the new definition,
re-assemble, and your done! I noticed that MYMACS
does not contain an END statement, how come? The
answer to this one is also slick: with no END
statement included, if there ever comes a time that
you would rather COPY MYMACS.M68 to a file, you may
do so. If there was an END statement contained
within MYMACS, as soon as you copied in the file,
you would be at the "END" of your code!
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_Wrapping Up_
Perform the step above to be sure you understand
how to create a universal file. As the series
continues, we will begin to employ more and more of
the neat features of the Alpha Micro assembler, so
don't find yourself getting behind! Coming up in
the future will be number conversion routines,
block programming using the LNKLIT command, and
even file I/O! Also, as long as I keep getting
positive comments about this series I will continue
submitting the AAA. Input and suggestions are more
than welcome. I enjoy writing these article as long
as somebody gets something out of them. See you
next month. Bye!