LOGIC Apps/Logic-APPLE_II_APPS.iso/mac/LOGIC Apple II 5.25" Library - ProDOS 8/P8D001E.dsk/AH.TXT.16.txt

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                             APPLE II HISTORY
                             ===== == =======

                  Compiled and written by Steven Weyhrich
                    (C) Copyright 1991, Zonker Software

                           (PART 16 -- LANGUAGES)
                            [v1.0 :: 22 Jan 92]


PROGRAMS "R" US

     Nearly everyone reading this is already a programmer, on one level or
another.  Even if you don't know a "GOTO" from a "STA $C030", you already
know how to program something.  For the act of "programming" is nothing
more than giving instructions to a non-human device to have it carry out
what you want it to do.  The device that most of you already know how to
program is your automobile.  The act of giving those instructions may not
seem like programming to YOU; nevertheless in its strictest sense,
programming it is.  You want the car to go forward?  Set the transmission
to "D".  Go in reverse?  Use "R".  Of course, the programming needed to
operate an automobile is quite simple, and cannot be done in more than one
step at a time.  An example of a device that is more complicated to program
but does let you store up several instructions in advance is a VCR.  On the
VCR you instruct it to record a television broadcast that starts at 7:00 pm
and ends at 8:30 pm, on channel 6.  The more sophisticated VCR's can have
several programs set up in advance.  If you can operate a VCR in this
fashion (which is, admittedly, not always as easy as I have described), you
are a programmer.
     When it comes to the microcomputer, the process of programming (giving
it instructions on how to carry out a task) is somewhat more complicated.
This is primarily because the computer is far more flexible in its ability
to accept instructions and carry them out than is an automobile or VCR.
Devices attached to a computer can be manipulated by a program to do
something useful (print a letter several times, or perhaps read the outside
temperature and sound an alarm if it drops too low).  This flexibility,
plus the speed at which a computer can execute its instructions, makes it a
powerful tool for doing things that have previously taken much more effort
and time.  And as a project becomes more sophisticated, so also must the
programming acquire a similar level of sophistication.  The rate at which
computers, including the Apple II, have increased in capacity during the
past fifteen years has made it possible to design programs that can do
things that were not even dreamed possible back in the days of the 4K
Integer BASIC machine.
     An example of programming evolution on the Apple II was given during
Kansasfest in July of 1991.  To fully appreciate this narrative, you need
to know a little about an old Integer BASIC program, APPLEVISION.  This was
found on the DOS 3.2.1 System Master disk, and was a fun little display
that showed off the use of hi-res graphics.  It began by creating a simple
line drawing of a room, with a picture on the wall ("HOME SWEET HOME") and
a television set.  On the screen of the TV appeared a man who danced to the
tune of "Turkey In The Straw", which sounded on the built-in speaker.  It
ran repeatedly, until the user interrupted the program.  It was fascinating
at the time, since there was nothing in the program text that showed off
exactly HOW the hi-res effects were accomplished.  But things have gotten a
bit more complex as time has gone by:


     "Roger Wagner's keynote address featured a history of hypermedia
     which Roger set into action and left to run as he wandered
     offstage.  The history began with Bob Bishop's classic
     AppleVision, done in black and white on the original Apple II.
     Progressive screens enhanced the AppleVision image using
     subsequent incarnations of Apple II graphics (single
     hi-resolution, double hi-resolution, and the IIGS's Super
     Hi-Resolution modes).  Finally, thanks to a laserdisc player
     under HyperStudio's control and a video overlay card, Roger's
     image appeared within the television's screen and spoke to the
     audience, completing the introduction before turning the
     presentation back to Roger (returning from offstage)."<1>


     To follow the programming progress that has made such magic possible,
we will begin with the first two built-in high-level languages for the
Apple II, Integer BASIC and Applesoft, and move on to a briefer discussion
of some of the other languages that have been available over the years.
Next will be a summary of various 6502 and 68816 assemblers that Apple
programmers have used over the years.  Finally, I will present an
introduction to "hyper-programming".


FUNDAMENTALS OF PROGRAMMING

     A programming language has the standards to translate "what I want"
into commands that the computer understands.  To do so, it must take some
human language and convert it into the binary dialect of the computer on
which it is executed.
     Computer languages usually come in one of two different types:
"interpreted" and "compiled".  A language that functions as an interpreter
takes the text of the program and translates it at the time of execution
into commands the computer can understand.  A compiled program, on the
other hand, has already had the program text translated into executable
code BEFORE it is run, usually including some extra code needed to carry
out necessary functions of input, output, and calculations.  As such, an
interpreted program usually runs more slowly, but has the advantage of
being easier to modify and re-run without the delay of first re-compiling.
A compiled program will ordinarily run faster, but may use more memory than
an equivalent interpreted program.
     Languages are also given the designation of being "high-level" or
"low-level", depending on how close they are to the base language of the
computer on which they run.  The lowest level of computer programming is at
the level of the bytes understood as commands by the microprocessor.  This
"machine language" is typically not very understandable to humans.  A
low-level language more often used by programmers is "assembly language".
This uses commands somewhat more understandable ("LDA $24" means "load the
accumulator with the contents of memory location $24") and are then
assembled (actually compiled) it into machine-readable code.  Assembly
language is very powerful, since it works on the byte level of the
computer.  However, as a low-level language it can be very complicated and
requires an intimate understanding of the function of the computer.
     As a language becomes more "high-level", it is easier for humans to
read, but requires more effort from its interpreter or compiler to
translate it into the native language of the computer.


INTEGER BASIC

     This was the first language available for general use on the Apple II
(aside from assembly, which will be dealt with later).  Most of the details
concerning its development have already been covered in Part 3 of this
History.  It was a quick, compact language, and its creation was an example
of programming directly in machine language (since Steve Wozniak, the
author, had no assembler available to use).  Its disadvantage was the lack
of easy access to floating point operations, and it lacked some string
handling functions.  Apple II users, especially those who wanted to produce
programs that could be used in business applications, wanted something more
powerful to use.
     Despite its limitations, Integer BASIC was a language that had a
fanatically loyal following.  For those thousands who purchased Apple II's
from June 1977 to June 1979, this was the only programming language
available, and it took on a status similar to that of a beloved first-born
child.  Games, utilities, and even some simple business-use programs were
written using Wozniak's hand-assembled masterpiece, and those who followed
the pages of Call-A.P.P.L.E. magazine learned much about the internals of
the language.  With the disassembler built into the Monitor, people tore
Integer BASIC apart to learn how it worked, and to make it work better.
Val Golding, the editor of Call-A.P.P.L.E., even wrote a series of columns
in 1979 entitled "So Who Needs Applesoft?"  These articles showed how to
simulate some of the more advanced features of Applesoft in this older
BASIC.  A.P.P.L.E. even sold (under license agreement with Apple Computer)
"Integer BASIC +", a relocatable RAM version of the original ROM BASIC.  It
had all the features of the original language, plus a "USER" command, the
ability to easily do four direction scrolling on the text and lo-res
screens, easy printing of ASCII characters, and improved error handling.<2>
     Apple never released a comprehensive reference manual for Integer
BASIC.  The only manual available for it was primarily a tutorial (and a
general introduction to using a computer).  The "Apple II BASIC Programming
Manual" didn't even call it "Integer BASIC", but referred to the language
as "Apple BASIC".  It gave most of its programming examples in the form of
segments of a graphics and sound demo that created a lo-res ball bouncing
off the sides of the screen.<3>
     With the many programs available that were written in Integer BASIC,
it was almost a necessity for Apple to offer a means for Apple II Plus
users to be able to run the older software.  The Integer Firmware card made
this "backward compatibility" possible.  This was especially important in
the early days of the II Plus, when there was little new software available
to use with Applesoft.


APPLESOFT I

     Although Wozniak had written some floating point routines into the
Integer Basic ROM, Apple II users needed a version of Basic that would make
floating point math easier to do, particularly for business use (where the
number to the right of the decimal point is as important as the one to
left).  Apple decided to license a 6502 version of a floating point BASIC
from Microsoft Corporation.  Back in 1977, Microsoft was producing BASIC
interpreters for nearly every microcomputer that was produced.  The version
Apple purchased was almost identical to the MITS extended BASIC that
Microsoft had previously written for the Altair 8800.<4>,<5>
     This BASIC was named "Applesoft", and was released in November of 1977
on cassette.  It was loaded as a 10K program that looked to the computer
just like an Integer BASIC program, though only a small part of it really
was.  To make it easy to load and start from cassette, the Applesoft
interpreter was attached to the end of a short Integer BASIC program.  When
the Integer program was run, it poked some values into memory and jumped to
the start of the machine language section, which relocated the Applesoft
interpreter to the lower part of memory (at $800), just after the memory
that held the screen display.
     Using this version of Applesoft (which later became known as
Applesoft I) could be frustrating.  It took several minutes to load from
the cassette tape, and it was not dependable.  If the wrong key was pressed
while entering or running an Applesoft program, the program that was being
run could be wiped out, and the Applesoft interpreter itself would have to
be reloaded from cassette.  However, few users knew how to make use of the
floating point routines that Wozniak had written into the Integer ROM, so
this unreliable Applesoft BASIC became the only practical means of doing
floating point math on the Apple II.
     Aside from the reliability issue, another difficulty with Applesoft
involved hi-resolution graphics.  Although the Apple II was capable of
displaying it, the Applesoft interpreter extended up into the memory used
by the hi-res screen, and so prevented its use.  Furthermore, this early
version had no built-in commands to manage hi-res graphics.<5>
     Applesoft I came with a manual that was 8 1/2 inches by 11 inches in
size, and sported a blue cover with square glued binding.<6>  This came to
be known as the "blue book" (recall that the reference book for the
computer itself was affectionately known as the "red book").  When starting
the interpreter after loading it from the cassette, a screen was display
announcing that Applesoft was copyright 1977 by Apple and Microsoft.  It
then asked the user for the memory size of his computer, and gave options
of allowing either LET and REM statements OR the use of lo-res graphics.
The names of the lo-res graphics commands were very different from those
that existed in Integer BASIC (and in the later versions of Applesoft).
The commands were:

PLTG           = Go to lo-res graphics mode
TEX            = Go to text mode
PLTC N         = Set color to N (0-15)
PLTP X,Y       = Plot square at X,Y
PLTH X1,X2,Y   = Plot horizontal line from X1 to X2 at Y
PLTV Y1,Y2,X   = Plot vertical line from Y1 to Y2 at X

     There was a note about these commands in the reference card included
with Applesoft I that warned about using graphics coordinates only between
0 and 39, or a program could "self-destruct".   Apparently it lacked the
error checking that could prevent the plotting of lines from spilling over
into the text of the Applesoft program itself.<6>,<7>
     The A.P.P.L.E. user group published a patch in 1978 that allowed
programmers to avoid the question about using LET and REM statements versus
lo-res graphics, and use the graphics only.  The author of the patch
pointed out that the LET statements were not necessary ("A = 3" worked just
as well as "LET A = 3").  The REMark statements could be simulated by
putting them at the end of a GOTO line (where they were ignored by the
interpreter), and the GOTO could just jump to the following line:

   530 GOTO 540: REM LINE 540 SETS VARIABLE N.
   540 N = 2

     Additional patches were made available for some of the other bugs
found in Applesoft I.<8>


APPLESOFT II

     In spring 1978, Randy Wigginton and some others at Apple made some
needed revisions to Applesoft.  Using a cross-assembler running on a North
Star Horizon (Z-80) microcomputer, they fixed the known bugs and added
other commands to control features unique to the Apple II.  These commands
included the ones needed to draw and manipulate hi-res graphics.  Also, the
lo-res graphics commands were renamed to be more consistent with the
equivalent commands in Integer BASIC (GR, HLIN, VLIN, etc.)  This version
was called "Applesoft II", and eventually it was available in five forms:
Cassette RAM and Diskette RAM (which loaded to the same memory locations
that interfered with hi-res graphics as did Applesoft I), Firmware card
ROM, Language card RAM, and finally main board ROM (in the Apple II Plus).
     When Applesoft II was started up from cassette or diskette versions,
the display screen now showed a copyright date of 1978 by Apple Computer,
Inc., and 1976 by Microsoft (which may be either their copyright date for
the original Microsoft BASIC, or possibly for Microsoft's first 6502
version).<6>  This RAM version of Applesoft II used memory from $800-$2FFF,
and the Applesoft BASIC program itself was loaded beginning at $3000.  When
the versions that came on ROM and for the Language Card RAM were released,
the BASIC program could load at $800, and much more memory was available
for it.  Some of this extra space (in high memory) was reclaimed by DOS
when the Disk II was released, however.<5>
     Applesoft in the original IIe was unchanged from the II Plus version.
When the IIc was introduced in 1984, however, Apple programmers had
cautiously made a few useful changes to the language:

     o Input processing was changed to allow lowercase entry of Applesoft
       commands (they were translated into uppercase)
     o Screen output commands (PRINT, TAB, HTAB, etc.) were modified to
       more properly handle the 80-column screen
     o Program lines (when LISTed) were changed to begin in column 2,
       making screen editing easier
     o All of the cassette tape routines (LOAD, SAVE, SHLOAD, STORE, and
       RECALL) were removed, since the hardware did not support cassette
       I/O.  The keywords were still in the token table, but now pointed to
       the same memory vector as the ampersand ("&") command.
     o Patches were made to the lo-res graphics commands (GR, HLIN, VLIN,
       PLOT, and SCRN) to work with double lo-res graphics.  However, a bug
       was introduced that allowed PLOTting vertically to areas outside of
       the double lo-res graphics screen, which would land right in the
       beginning of the $800 space where the Applesoft program text was
       located (similar to the "plot" bug in Applesoft I).

     When the Apple IIe Enhanced ROMs were made available, Applesoft in
those ROMs had undergone some similar modifications.  All the above IIc
changes were added, with the exception that double lo-res graphics
capability was NOT added (lack of ROM space), and the cassette I/O commands
were NOT removed (since the cassette input and output port was still
present).
     The version of Applesoft on the Apple IIGS closely resembled the
Apple IIc variant, the only exception being a fix of the double lo-res
PLOTting bug.  However, a bug in the SCRN function that applied to double
lo-res mode was NOT fixed.  No changes to Applesoft from the IIc version
appeared in the Apple IIc Plus.<9>
     The manuals written for Applesoft II were far more comprehensive than
either the older "Blue book" or the Integer BASIC manual.  It gave not only
programming examples for each of the commands, but included much more
information about the various ways in which each Applesoft statement could
be used.  It also mentioned some of the differences between Applesoft and
Integer (for those who wanted to convert their older programs), and gave a
little information about the internals of Applesoft to aid in creating
machine language additions to the language.  Curiously, the manuals that
have been reprinted even as late as 1990 by Addison-Wesley have included an
odd cautionary note to programmers.  In a section in the index about
"reserved words" (words reserved as Applesoft commands), it advises against
using "XPLOT" as a variable name, stating that "it is a reserved word that
does not correspond to a current Applesoft statement."  What is apparently
meant by this comment is that at one time Apple intended to extend the
language and add another command "XPLOT" to it, probably working with HPLOT
in the same way that XDRAW complements DRAW in doing hi-res graphics.
Examination of the command table within the Applesoft interpreter shows
thereis NO entry labeled "XPLOT", and a disassembly of the interpreter
shows NO preliminary code to support the command.  Somehow this precaution
persisted to the present day and has never been removed, even though it is
extremely unlikely that Applesoft will ever be upgraded.<10>
     Particularly helpful for programmers was the foresight to include a
simple extension called the "ampersand hook".  If Applesoft came across the
"&" symbol while interpreting a line, it jumped to a known location in
memory and left it to the programmer to insert the correct code to add a
machine language extension to the language.  With the publication of
important information about the internals of Applesoft in 1980, assembly
language programmers could now add statements to do things that could not
be done with the language as it was originally created.  Music, extended
graphics, IF-THEN-ELSE logic, and even the missing "XPLOT" command could be
added to the language.  The only limits were the author's imagination (and
available memory).
     The importance of Applesoft as an influence to productivity on the
Apple II cannot be overstated.  Since the release of the Apple II Plus in
1979, every variety of Apple II has contained Applesoft in virtually an
unchanged form.  This has made it possible for anybody to write programs
that ALL other Apple II users will be able to use, since the language does
not have to be purchased or added.  If there were thousands of Integer
BASIC programs from the two years when Integer Apple II's were produced
exclusively, there are hundreds of thousands of Applesoft programs that
appeared over that subsequent thirteen years.  Even today, it is not
uncommon for an applications program to include a configuration module
written in Applesoft using the disk commands available with BASIC.SYSTEM in
ProDOS.  It is often faster to write such a program in BASIC, and the
author knows without a doubt that his customer will be able to run it.


APPLESOFT 3 (?)

     In 1979 there were rumors at the West Coast Computer Faire about an
enhancement to Applesoft II that was in the works at Apple.  It would
possibly be called Applesoft 3, and would be as much of an enhancement over
Applesoft II as that version was to Applesoft I.  Supposedly it was
intended to merge DOS and BASIC, and would include such powerful functions
as IF-THEN-ELSE, PRINT USING, WINDOW, and VIEW PORT.  It was predicted to
be a RAM version only, and would be about 24K in size.  Knowing the events
that actually followed, this rumored BASIC was probably the "Business
Basic" released with the Apple III, rather than an enhancement for the
Apple II.<11>


+++++++++++++++++++++++++++++++++++

NEXT INSTALLMENT:  Languages, cont.

+++++++++++++++++++++++++++++++++++

                                   NOTES


     <1> Doms, Dennis.  "KansasFest 1991", A2-CENTRAL, Sep 1991, p. 7.57.

     <2> -----.  (ad), PEEKING AT CALL-A.P.P.L.E., VOL 2, 1979, p. 62.

     <3> -----.  APPLEII BASIC Programming Manual, 1978, 1979, 1980, 1981.

     <4> Chien, Philip.  "The First Ten Years: A Look Back", THE APPLEII
         Review, Fall/Winter 1986, p. 12.

     <5> Golding, Val J.  "Applesoft From Bottom To Top", CALL-A.P.P.L.E.
         IN DEPTH #1, 1981, p. 8.

     <6> Bernsten, Jeff.  GEnie, A2 ROUNDTABLE, Apr 1991, Category 2, Topic
         16.

     <7> Arkley, John.  (personal telephone call), Sep 9, 1991.

     <8> -----.  "Apple Patches", PEEKING AT CALL-A.P.P.L.E., VOL 1, 1978,
         p. 40.

     <9> Weyhrich, Steven.  "Applesoft Miscellaneous Information",
         APPLESOFT CONCORDANCE V1.0, Dec 1989.

     <10> Kamins, Scott.  "Appendix D  Reserved Words", APPLESOFT BASIC
         PROGRAMMER'S REFERENCE MANUAL, 1982, 1983.

     <11> Aldrich, Darrell.  "The Computer Faire And The Apple", PEEKING AT
         CALL-A.P.P.L.E., VOL 2, 1979, p. 158.