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Model 100 Tokenizer in C

An external "tokenizer" for the TRS-80 Model 100 BASIC language. Converts BASIC programs in ASCII text (.DO) to executable BASIC (.BA) on a host machine. Useful for large programs which the Model 100 cannot tokenize due to memory limitations.

$ cat FOO.DO
10 ?"Hello!"

$ tokenize FOO.DO 
Tokenizing 'FOO.DO' into 'FOO.BA'

$ hd FOO.BA
00000000  0f 80 0a 00 a3 22 48 65  6c 6c 6f 21 22 00        |....."Hello!".|
0000000e

A screenshot of running the FOO.BA program on a Tandy 102 (emulated via Virtual T)

This program creates an executable BASIC file that works on the Model 100, the Tandy 102, Tandy 200, Kyocera Kyotronic-85, and Olivetti M10. Those five machine have identical tokenization. It does not (yet) work for the NEC PC-8201/8201A/8300 whose N82 BASIC has a different tokenization.

Additionally, this project provides a decommenter and cruncher (whitespace remover) to save bytes in the tokenized output. This allows one to have both well-commented, easy to read source code and a small executable size.

Introduction

The Tandy/Radio-Shack Model 100 portable computer can save its BASIC files in ASCII (plain text) or in a “tokenized” format where the keywords — such as FOR, IF, PRINT, REM — are converted to a single byte. The Model 100 automatically tokenizes an ASCII program when it is LOADed so that it can be RUN or SAVEd. The tokenized format saves space and loads faster.

The problem

Programs for the Model 100 are generally distributed in ASCII format which is good for portability and easy transfer. However, ASCII files have downsides:

  1. RUNning an ASCII program is quite slow because the Model 100 must tokenize it first.

  2. Large programs can run out of memory (?OM Error) when tokenizing on the Model 100 because both the ASCII and the tokenized versions must be in memory simultaneously.

A screenshot of an OM Error after attempting to tokenize on a Tandy 102

The solution

This program tokenizes on a host computer before downloading to the Model 100.

File extension terminology

Tokenized BASIC files use the extension .BA. ASCII formatted BASIC files should be given the extension .DO so that the Model 100 will see them as text documents.

Click for details on filename extensions
    Machine Memory Map ASCII BASIC Tokenized BASIC
    Generic .DO .BA
    Model 100 / 102 .100 .BA1
    Tandy 200 .200 .BA2
    NEC PC-8201 .NEC.DO .BA0, .NEC.BA
    Olivetti M10 .M10.DO .B10, .M10.BA
    Kyocera Kyotronic-85 .KYO.DO .B85, .KYO.BA

    The primary two filename extensions are:

    • .DO This is the extension the Model 100 uses for plain text BASIC files, but in general can mean any ASCII text document with CRLF1 line endings.
    • .BA On the Model 100, the .BA extension always means a tokenized BASIC program. However, many ".BA" files found on the Internet are actually in ASCII format. Before the existence of tokenizers like this, one was expected to know that ASCII BASIC files had to be renamed to .DO before downloading to a Model 100.

    BASIC programs that use PEEK, POKE, or CALL typically only work on one specific model of portable computer, even when the BASIC language and tokenization is identical. (The only two models which have the same memory map are the Model 100 and and Tandy 102.) Using POKE or CALL on the wrong model can crash badly, possibly losing files. To avoid this, when sharing BASIC programs over the network, filename extensions are sometimes used to indicate which model a program will work on:

    • .100 An ASCII BASIC file that includes POKEs or CALLs specific to the Model 100 or Tandy 102.

    • .200 An ASCII BASIC file specific to the Tandy 200.

    • .NEC (or .NEC.DO) An ASCII BASIC file specific to the NEC PC-8201 portables.

    • .BA1 A tokenized BASIC file specific to the Model 100/102.

    • .BA2 A tokenized BASIC file specific to the Tandy 200.

    • .BA0 (or .NEC.BA) A tokenized BASIC file specific to the NEC portables.

    It is not yet clear what extensions are used to denote the Kyotronic-85 and M10. Hackerb9 suggests:

    • .KYO or .KYO.DO An ASCII BASIC file that includes POKEs or CALLs specific to the Kyocera Kyotronic-85.
    • .M10 or .M10.DO An ASCII BASIC file specific to the Olivetti M10.
    • .B85 or .KYO.BA A tokenized BASIC file specific to the Kyotronic-85.
    • .B10 or .M10.BA A tokenized BASIC file specific to the M10.

Programs in this project

  • tokenize: A shell script which ties together all the following tools. Most people will only run this program directly.

  • m100-tokenize: Convert M100 BASIC program from ASCII (.DO) to executable .BA file.

  • m100-sanity: Clean up the BASIC source code (sort lines and remove duplicates).

  • m100-jumps: Analyze the BASIC source code and output a list of lines that begin with a comment and that are referred to by other lines in the program. Input should have been run through m100-sanity.

  • m100-decomment: Modify the BASIC source code to remove REM and ' comments except it keeps lines mentioned on the command line (output from m100-jumps). This can save a lot of space if the program was well commented.

  • m100-crunch: Modify the BASIC source code to remove all whitespace in an attempt to save even more space at the expense of readability.

Compilation & Installation

Presuming you have flex installed, just run make to compile.

$ git clone https://github.com/hackerb9/tokenize
$ make
$ make install
Optionally, you can compile by hand 
 flex m100-tokenize.lex  &&  gcc lex.tokenize.c

Flex creates the file lex.tokenize.c from m100-tokenize.lex. The main() routine is defined in m100-tokenize-main.c, which is #included by m100-tokenize.lex.

Usage

One can either use the tokenize wrapper or run the executables manually.

The tokenize wrapper

The "tokenize" script is easiest. By default, the output will be exactly the same, byte for byte, as a .BA file created on actual hardware.

Synopsis

    tokenize INPUT.DO [ OUTPUT.BA ]
    tokenize [ -d | --decomment ] INPUT.DO [ OUTPUT.BA ]
    tokenize [ -c | --crunch ] INPUT.DO [ OUTPUT.BA ]

    The -d option decomments before tokenizing.

    The -c option decomments and removes all optional whitespace before tokenizing.

Example 1: Simplest usage: tokenize filename

$ tokenize PROG.DO
Tokenizing 'PROG.DO' into 'PROG.BA'
Click to see more examples

    Example 2: Overwrite or rename

    $ tokenize PROG.DO
Output file 'PROG.BA' is newer than 'PROG.DO'. 
Overwrite [yes/No/rename]? R
Old file renamed to 'PROG.BA~'

    Example 3: Crunching to save space: tokenize -c

    $ wc -c M100LE.DO 
17630 M100LE.DO

$ tokenize M100LE.DO 
Tokenizing 'M100LE.DO' into 'M100LE.BA'

$ wc -c M100LE.BA
15667 M100LE.BA

$ tokenize -c M100LE.DO M100LE-crunched.BA
Decommenting, crunching, and tokenizing 'M100LE.DO' into 'M100LE-crunched.BA'

$ wc -c M100LE-crunched.BA
6199 M100LE-crunched.BA

    In this case, using tokenize -c reduced the BASIC executable from 16 to 6 kibibytes, which is quite significant on a machine that might have only 24K of RAM. However, this is an extreme example from a well commented program. Many Model 100 programs have already been "decommented" and "crunched" by hand to save space.

      Tip: When distributing a crunched program, it may be a good idea to also include the original source code to make it easy for people to learn from, debug, and improve it.

Running m100-tokenize and friends manually

If one decides to not use the tokenize script, certain programs should usually be run to process the input before the final tokenization step, depending upon what is wanted. m100-sanity is strongly recommended. (See Abnormal code below.)

flowchart LR;
m100-sanity ==> m100-tokenize
m100-sanity ==> m100-jumps ==> m100-decomment
m100-decomment --> m100-crunch --> m100-tokenize
m100-decomment --> m100-tokenize
Loading
Programs used Effect Same as
m100-sanity
m100-tokenize		 Identical byte-for-byte to a genuine Model 100 tokenize
m100-sanity
m100-jumps
m100-decomment
m100-tokenize		 Saves RAM by removing unnecessary comments tokenize -d
m100-sanity
m100-jumps
m100-decomment
m100-crunch
m100-tokenize		 Saves even more RAM, removing whitespace tokenize -c
m100-tokenize Abnormal code is kept as is
Click to see more details about running these programs manually

    m100-tokenize synopsis

    m100-tokenize [ INPUT.DO [ OUTPUT.BA ] ]

    Unlike tokenize, m100-tokenize never guesses the output filename. With no files specified, the default is to use stdin and stdout so it can be used as a filter in a pipeline. The other programs -- m100-sanity, m100-jumps, m100-decomment, and m100-crunch -- all have the same syntax taking two optional filenames.

    Example usage of m100-tokenize

    When running m100-tokenize by hand, process the input through the m100-sanity script first to correct possibly ill-formed BASIC source code.

    m100-sanity INPUT.DO | m100-tokenize > OUTPUT.BA

    The above example is equivalent to running tokenize INPUT.DO OUTPUT.BA.

    Example usage with decommenting

    The m100-decomment program needs help from the m100-jumps program to know when it shouldn't completely remove a commented out line, for example,

    10 REM This line would normally be removed
20 GOTO 10   ' ... but now line 10 should be kept.

    So, first, we get the list of line numbers that must be kept in the variable $jumps and then we call m100-decomment passing in that list on the command line.

    jumps=$(m100-sanity INPUT.DO | m100-jumps)
m100-sanity INPUT.DO | 
    m100-decomment - - $jumps | 
	m100-tokenize > OUTPUT.BA

    The above example is equivalent to running tokenize -d INPUT.DO OUTPUT.BA.

    Note that m100-decomment keeps the entire text of comments which are listed by m100-jumps with the presumption that, as targets of GOTO or GOSUB, they are the most valuable remarks in the program. (This behaviour may change in the future.)

    Example output after decommenting but before tokenizing:

    10 REM This line would normally be removed
20 GOTO 10

    Example usage with crunching

    The m100-crunch program removes all optional space and some other optional characters, such as a double-quote at the end of a line or a colon before an apostrophe. It also completely removes the text of comments which may have been preserved by m100-decomment from the m100-jumps list. In short, it makes the program extremely hard to read, but does save a few more bytes in RAM.

    jumps=$(m100-sanity INPUT.DO | m100-jumps)
m100-sanity INPUT.DO | 
    m100-decomment - - $jumps | 
	m100-crunch | 
	m100-tokenize > OUTPUT.BA

    The above example is equivalent to running tokenize -c INPUT.DO OUTPUT.BA.

    Example output after crunching but before tokenizing:

    10REM
20GOTO10

    An obscure note about stdout stream rewinding

    After finishing tokenizing, m100-tokenize rewinds the output file in order to correct the PL PH line pointers. Rewinding fails if the standard output is piped to another program. For example:

    1. m100-tokenize FOO.DO FOO.BA
    2. m100-tokenize <FOO.DO >FOO.BA
    3. m100-tokenize FOO.DO | cat > FOO.BA

    Note that (1) and (2) are identical, but (3) is slightly different.

    In example 3, the output stream cannot be rewound and the line pointers will all contain "**" (0x2A2A). This does not matter for a genuine Model T computer which ignores PL PH in a file, but some emulators are known to be persnickety and balk.

    If you find this to be a problem, please file an issue as it is potentially correctable using open_memstream(), but hackerb9 does not see the need.

Click for details on creating abnormal .BA files.

    Abnormal code

    The tokenize script always uses the m100-sanity program to clean up the source code, but one can run m100-tokenize directly to purposefully create abnormal, yet valid, .BA files. These programs cannot be created on genuine hardware, but will run.

    Here is an extreme example.

    Source code for "GOTO 10" by hackerb9

    1 I=-1
10 I=I+1: IF I MOD 1000 THEN 10 ELSE I=0
10 PRINT: PRINT
10 PRINT "This is line ten."
10 PRINT "This is also line ten."
5  PRINT "Line five runs after line ten."
10 PRINT "Where would GOTO 10 go?"
15 PRINT "  (The following line is 7 GOTO 10)"
7 GOTO 10
8 ERROR "Line 8 is skipped by GOTO 10."
10 PRINT: PRINT "It goes to the *next* line ten!"
10 FOR T=0 TO 1000: NEXT T
10 PRINT "Exceptions: Goes to *first* line ten"
10 PRINT "  if the current line is ten, or"
10 PRINT "  if a line number > 10 is seen."
10
10 'Shouldn't 10 GOTO 10 go to itself?
10 'It shouldn't have to search at all.
10 'Maybe it's a bug in Tandy BASIC?
10 'Perhaps it checks for (line >= 10)
10 'before it checks for (line == 10)?
10
10 'BTW, >= is one less op than >.
10 'On 8085, >= is CMP then check CY==0.
10 'But > also requires checking Z==0.
10
10 PRINT
10 PRINT "The next line is 9 GOTO 10. This time"
10 PRINT "it goes to the FIRST line ten, because"
10 PRINT "line 20 comes before the next line ten."
9 GOTO 10
20 ERROR "Line 20 is never reached, but it has an effect because 20>10."
10 ERROR "This is the final line ten. The previous GOTO 10 won't find it because line 20 comes first."
10
15
20 
0 PRINT "This program examines how"
1 PRINT "Model T computers run"
2 PRINT "degenerate tokenized BASIC."
3 PRINT "Trying to load it as a .DO"
4 PRINT "file will not work as"
5 PRINT "Tandy BASIC corrects issues"
6 PRINT "such as duplicate line numbers"
7 PRINT "and out of order lines."
8 PRINT "Please use hackerb9's"
9 PRINT "pre-tokenized GOTO10.BA."

    To run this on a Model 100, one must download the tokenized BASIC file, GOTO10.BA, which is created from GOTO10.DO like so:

    m100-tokenize GOTO10.DO

Machine compatibility

Across the eight Kyotronic-85 sisters, there are actually only two different tokenized formats: "M100 BASIC" and "N82 BASIC". This program (currently) works only for the former, not the latter.

The three Radio-Shack portables (Models 100, 102 and 200), the Kyocera Kyotronic-85, and the Olivetti M10 all share the same tokenized BASIC. That means a single tokenized BASIC file might work for any of those, presuming the program does not use CALL, PEEK, or POKE. However, the NEC family of portables -- the PC-8201, PC-8201A, and PC-8300 -- run N82 BASIC. A tokenized N82 BASIC file cannot run on an M100 computer and vice versa, even for programs which share the same ASCII BASIC source code.

Checksum differences are not a compatibility problem

The .BA files generated by tokenize aim to be exactly the same, byte for byte, as the output from tokenizing on a Model 100 using LOAD and SAVE. There are some bytes, however, which can change and should be ignored when testing if two tokenized programs are identical.

Click to read details on line number pointers...

    A peculiar artifact of the .BA file format is that it contains pointer locations offset by where the program happened to be in memory when it was saved. The pointers in the file are never used as they are recalculated when the program is loaded into RAM.

    To account for this variance when testing, the output of this program is intended to be byte-for-byte identical to:

    1. A Model 100
    2. that has been freshly reset
    3. with no other BASIC programs on it
    4. running LOAD "COM:88N1" and SAVE "FOO" while a host computer sends the ASCII BASIC program over the serial port.

    While the Tandy 102, Kyotronic-85, and M10 also appear to output files identical to the Model 100, the Tandy 200 does not. The 200 has more ROM than the other Model T computers, so it stores the first BASIC program at a slightly different RAM location (0xA000 instead of 0x8000). This has no effect on compatibility between machines, but it does change the pointer offset.

    Since two .BA files can be the identical program despite having different checksums, this project includes the bacmp program, described below.

Why Lex?

This program is written in Flex, a lexical analyzer, because it made implementation trivial. The tokenizer itself, m100-tokenize, is mostly just a table of keywords and the corresponding byte they should emit. Flex handles special cases, like quoted strings and REMarks, easily.

The downside is that one must have flex installed to modify the tokenizer. Flex is not necessary to compile on a machine as flex generates portable C code. See the tokenize-cfiles.tar.gz in the github release or run make cfiles.

Miscellaneous notes

  • Tokenized BASIC files are binary files, not ASCII and as such cannot be transferred easily using the builtin TELCOM program or the LOAD "COM:" or SAVE "COM:" commands. Instead, one must use a program such as TEENY which can transfer 8-bit data.

  • To save in ASCII format on the Model 100, append , A:

    save "FOO", A

  • This program accepts line endings as either CRLF (standard for a Model 100 text document) or simply LF (UNIX style).

Testing

Run make check to test this tokenizer on some sample Model 100 programs including some strange ones designed specifically to exercise peculiar syntax. The program bacmp is used to compare the generated .BA file with one created on hackerb9's Tandy 200.

For example, SCRAMB.DO has input that is scrambled and redundant to check if m100-sanity is working correctly.

20 GOTO 10
10 GOTO 10
10 PRINT "!dlroW ,olleH"

bacmp: BASIC comparator

The included bacmp.c program may be useful for others who wish to discover if two tokenized BASIC files are identical. Because of the way the Model 100 works, a normal cmp test will fail. There are pointers from each BASIC line to the next which change based upon where the program happens to be in memory. The bacmp program handles that by allowing line pointers to differ as long as they are offset by a constant amount.

Note that generating correct line pointers is actually unnecessary in a tokenizer; they could be any arbitrary values. The Model 100 always regenerates the pointers when it loads a .BA file. However, some emulators insist on having them precisely correct, so this tokenizer has followed suit.

More information

Known Bugs

  • None known. Reports are gratefully accepted.

Alternatives

Here are some other ways that you can tokenize Model 100 BASIC when the source code and the tokenized version won't both fit in the M100's RAM.

Footnotes

  1. CRLF means Carriage Return, Line Feed. That is, 0x0D 0x0A. ↩

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Tokenizer for Model 100 BASIC

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flex compression tokenizer basic-programming cruncher trs-80model100 model100 tandy200 kyocera-85

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