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Fitted Modula-2 Version 2.0

(C) Copyright 1987,1988 Fitted Software Tools.
All rights reserved.

Fitted Software Tools
P.O.Box 867403
Plano, TX 75086
BBS 214/517-4629




All the information in this document is believed to be correct at the
time of publication. We do, however, reserve the right to make any
changes in product specifications and/or availability without notice.

IBM is a registered trademark of International Business Machines

Introduction 2

Chapter 1


Thank you for your interest in our Modula-2 compiler.

This system features a Modula-2 compiler with an integrated editor and
"make" facility, a program linker, a makefile generator, and an
execution profiler.

The compiler generates code for the Intel 8086 "huge" or "large"
memory model: In the "huge" memory model, each module has its own data
and code segment, each of which can be up to 64k in size; In the
"large" memory model, all the modules' static data is combined into a
single data segment. In either model, pointers are 4 bytes long and
all the leftover memory is available for the "heap". More restrictive
memory models are not currently supported.

All the library and runtime support source code is available to our
registered users (see Shareware).

We hope that our effort will prove itself worthy of your support.

Introduction 3

1.1 Hardware requirements

This system will run on IBM PC, PC/AT, or compatible systems with at
least 512K of RAM, two double sided floppy disk drives and a
monochrome display adapter, color graphics adapter or equivalent.

A hard disk and 640K of RAM are, however, recommended.

1.2 Software requirements

This system requires DOS version 2.0 or later.

No other software is required to use this system, but you will need an
assembler if you intend to modify one of the runtime support modules:
M2Reals (floating point support), M2Longs (LONG arithmetic) or M2Procs
(coroutine handling).

1.3 For users upgrading to release 2

This is, in a nutshell, what is new in release 2.0.

LONGREALs: You now have a choice of REAL size. Release 1.x supported
only the 4 byte real number format, which provided about seven digits
of accuracy. The LONGREAL format is 8 bytes and has about 15 digits
of accuracy. The tradeoff, of course, is time. But, if you need
accurate results in a short time, then...

8087 support: M2Reals, Mathlib0 and LMathLib0 (MathLib0 for LONGREALs)
will use the 8087/80287 math coprocessor if one is present. Inline
generation of 8087 code is not available at this time. The inline
assembler supports all the 8087 mnemonics, but with some

OBJ file generation: You may now instruct the compiler to generate DOS
compatible OBJ files. Please refer to the chapter on OBJ files for
more details.

Introduction 4

Of special importance the international users, is the fact that the
editor now accepts characters > 7FX. Indent and unindent commands were
also added to the editor, as well as 43 or 50 line display support.

The module RealConversions was added to the system. You can finaly
convert floating point numbers to fixed decimal notation!

This is the most visible stuff. There are, of course, many more minor
enhancements in release 2.

Of particular importance (it may affect your code!):

The compiler now generates checks for NIL pointers, when the $T
directive is in effect. Also, Storage.DEALLOCATE now sets the
pointer passed to it to NIL.

In release 1 there were some problems with the implementation of
type compatibility between CARDINAL and INTEGER: The compiler was
more strict than the language definition called for. Some of
this was fixed along the way in release 1. We hope to have it
cured now. When the $R directive is in effect, the compiler
generates "range check code" on assignments between INTEGERs and
CARDINALs; basically, if the high order bit is on, the value is
out of range, regardless of which way you are going.

We owe an apology to many of the users that wrote in (or dialed up)
with good suggestions. Although some of these were implemented, many
were not, not because they were discarded, but because of the
unnavailability of resources (time, mostly!).

We hope that you will find this new release a worthy successor to what
we introduced a little over a year ago.

Software installation 5

Chapter 2

Software installation

Before starting, please print the file READ.ME, which provides a
description of every file in the distribution disks.

2.1 Theory

The library module TermIO (through which Terminal does its I/O)
requires that the ANSI.SYS driver be installed.

The executable files (MC.EXE, M2LINK.EXE, ...) should, for ease of
operation, be placed in a drive/directory named in the DOS PATH

The editor configuration file M2ED.CFG must be accessible through the

Both the compiler and the linker will use the environment variable
M2LIB to locate required library modules (the format for the M2LIB
entry matches that of the DOS PATH).

The environment variable M2MODEL may be set to 'HUGE' or 'LARGE',
after which you no longer have to tell the compiler what memory model
to compile for (unless you wish to override the environment
selection). IF M2MODEL is not set, the compiler, by default (and for
compatibility with version 1.0), assumes that you want to compile for
the HUGE model.

The compiler and utilities in this package do not keep many files open
simultaneously. If you set the FILES parameter in CONFIG.SYS to 10
you should not encounter any problems. For performance
considerations, you should also allocate more than the default number
of buffers for DOS: If you are running on a PC class machine, try
allocating 20 buffers in your CONFIG.SYS. On an AT class machine, try
64 buffers.


Software installation 6


This compiler is a memory hog -- you heard it here first! This is
neither good nor bad, simply an implementation decision. Source
modules being compiled, for example, are sucked into memory with a
single read system call.

Source files (either being compiled or edited) are loaded at the top
of available memory. This, of course clobbers the resident portion of
COMMAND.COM. Because this software was developed on a relatively slow
system, with a very slow hard disk, we decided that it would be a good
idea to, on request, preserve the resident portion of COMMAND.COM.

To enable the "COMMAND save" feature of the compiler, which will stop
it from clobbering the resident portion of COMMAND.COM, just add the
following line to your AUTOEXEC.BAT file:


where NN is the size of the resident portion of COMMAND.COM in K (18
for DOS 3.0).

MC clobbers the top of the memory space available for use during
initialization. Therefore, to find out the size of the resident
portion of COMMAND.COM, try the following procedure: start by setting
CMDSIZE to the size of COMMAND.COM. If now you execute MC, exit it,
and press the F3 key, DOS will still remember your MC command.
Decrement CMDSIZE and retry the MC test until the system forgets your
last command (COMMAND.COM had to be reloaded).

Because the compiler supports 2 different memory models, 2 different
sets of library object files (.M2O) are provided, one for each of the
memory models. If you are going to be using both memory models, keep
each of these sets of files in a different directory, and change the
M2LIB path according to the model in use. We use the following BAT
files to take care of this:

set M2LIB=C:\M2\LIB;C:\M2\LIBL

set M2LIB=C:\M2\LIB;C:\M2\LIBH

where \M2\LIB is the directory where all the DEF files reside,
\M2\LIBL contains the LARGE memory model M2O files,...

In the following discussion we will, for simplicity sake, assume that

Software installation 7

you will be using only one of the memory models.

2.2 Recommended setup for a system with 2 floppy drives

This whole system is too large to fit in a single 360k floppy.
Therefore, it is recommended that you build a "compiler" floppy and a
"utilities" floppy (you may combine them both in a 720k or 1.2Mb

On the compiler floppy, place the compiler (MC.EXE), all the library
definition modules (*.DEF), the file M2ED.CFG and DOS' COMMAND.COM.

The utilities floppy will take the rest of the system: the linker
(M2LINK.EXE), other .EXE files, and the library and runtime support
object files (*.M2O and *.BIN).

Assuming that you will use drive A for the compiler and utilities disk
and drive B as your work drive, add the following to your AUTOEXEC.BAT


If you follow these suggestions, you may use all the system's
capabilities. Just remember to swap the floppy in drive A before and
after invoking the linker from the compiler's menu.

2.3 Recommended setup for a hard disk system

Place the executable files (*.EXE) and M2ED.CFG in a directory
currently in the DOS search path, or in a new directory (ex: \MODULA2)
to be added to the PATH list. Example:


Make a directory for the library files (ex: \M2LIB) and copy all the
.DEF, .M2O and .BIN files to it. To the AUTOEXEC.BAT file add the


You will probably want to create a directory for your own reusable
library modules. This directory can be added to the M2LIB environment

Software installation 8

variable. Example:


You may keep your projects in their own, individual, directories.

A little tour through the system 9

Chapter 3

A little tour through the system

After you finish the installation as described above, please copy the
files identified as the "system tour files" in the READ.ME file to
your work disk or directory.

Because we do not know your particular system configuration, in the
following examples we will assume the worst possible scenario.
Therefore, some of the capabilities of this system will not be fully
exploited. Specifically, we will not invoke the linker or run the
programs from the compiler menu, neither will we invoke a DOS shell to
run DBG2MAP.

3.1 The tour

First, we will look at the unnatural case of compiling, linking and
running a program that works the first time around. Please execute
the following commands:


Well, that's it! Ready to run...


Now for the more usual case:


From the compiler menu, select 'C' for compile.

Gee, that was quick! Press RETURN to take a look at our errors...

The cursor is now positioned at the location of the first error.
Using the keys Ctrl-E (find next error) and Ctrl-P (find previous
error) you may visit all the errors flagged by the compiler. All the

A little tour through the system 10

while, the editor shows the error description on the top line of the
screen. But, going back to the first error...

We really confused the compiler when we mistakenly typed in '.'
instead of '..' in the range declaration. Move the cursor back (left
arrow key) to where the '.' is, type in another '.', and that should
fix that! As you will see as you type Ctrl-E, that single error
caused the compiler to dislike a few other things on that same line;
we will just ignore those errors and go on.

Go on to the next error location (line 22). This time, we should have
used a ']' but typed '}' instead. The backspace key will delete the
offending character; now, type the ']' in its place.

And that is that. Shall we try to compile the program again?

Press Alt-S to save the file, Alt-Q to leave the editor and, back at
the main menu, select 'C'.

More errors?!

These errors should have been detected during pass2 of the
compiler; If not, you may try to fix these errors and recompile,
or you may opt for loading and compiling the new file
BADSIEV1.MOD, which contains the earlier fixes.

Going back to the editor...

We find that we used the identifier 'cnt' which is undefined; we
really meant to use count. So, moving the cursor around with the
cursor keys and/or deleting characters with the backspace or delete
key, please replace 'cnt' by 'count'.

Searching for the next error...

The next error occured during the processing of the call to WriteCard.
What happened here is that WriteCard requires 2 parameters, the second
one being the size of the field to display. So, to fix it, let's
insert a comma after 'count' and some number (for example 'count,4').

Any more erors? No, that is it...

We now save the file (Alt-S), quit the editor (Alt-Q) and recompile

Now, the program should have compiled without errors. If not, you may
recompile BADSIEV2.MOD instead.

We may now quit the compiler (q).

By now, we have some program that has compiled clean (BADSIEVE,
BADSIEV1 or BADSIEV2). In what follows, we will assume all went well
and we have BADSIEVE.

A little tour through the system 11

If you look at the directory, you will see the new object module
created as a result of the previous exercise (BADSIEVE.M2O). The
compiler always writes its output to a file with the extension 'M2O'.

Let us link and test the program:


We use the /L option so that the line number information written out
by the compiler to the object file will be preserved by the linker.
We will need this information later.


A runtime error? And it gives us a PC location. Very informative, is
it not? How in the world are we supposed to fix the program based on
that? Do not dispair!

Looking at your directory, you will notice that the linker created 2

No, TYPEing BADSIEVE.DBG does not help, it just displays garbage. But
we have a utility called DBG2MAP that will convert the information in
that file to a DOS LINK compatible MAP file. Let's try it:


Now, using your favorite editor (or the editor in MC: MC BADSIEVE.MAP
and then E), look at the contents of BADSIEVE.MAP. In the last few
lines of the file, we have the line number information for BADSIEVE.
If you look up the line whose address is closest (but lower) to the PC
in the error message, you get the number of the line where the error
occured (line 22).

Let's see what happened...


Pick 'E' to go into the editor and, either move the cursor down to the
line indicated by your research, or let the editor find it with Alt-G.

So, what is the problem? Well, we declared the 'flag' array to have a
maximum index of 8190, but 'j' got bigger than that (the FOR loop will
increment 'j' up to the value of 10000).

You may fix the problem by deleting the '10000' and typing in its
place 'SIZE'.

Recompile the program, link it, and run it. Did it work? Good.

It is time for you to experiment on your own. But, before you do much
more, you may want to check out the Editor chapter of the

A little tour through the system 12


The Compiler 13

Chapter 4

The Compiler

In the Modula-2 language, as defined by Niklaus Wirth, identifiers may
be used before they are declared, except when they are used in another
declaration (this restriction does not apply to pointers). This
forces the compilation process to be done in at least two passes.

To avoid imposing unnecessary restrictions and, yet, provide
reasonable performance, the two pass approach was selected: During the
first pass, syntax analysis and declaration analysis are performed;
The second pass performs the semantic analysis and code generation.

The compiler has an integrated text editor. Should errors be
encountered, the editor is invoked at the end of the current compiler
pass (sooner, if an error is found during the processing of an import
list or if 20 errors are identified).

The compiler also has a built in "make" processor. A makefile must be
created before this process is invoked. Although you can create a
makefile using the editor, we recommend that you use the utility
provided for that purpose: GENMAKE (this utility may be invoked from
the compiler menu -- G).

The compiler can generate 2 different kinds of object files as
output. By default, M2O (stands for "Modula-2 Object") files are
generated. This file format is unique to this compiler, and it is
optimized for our requirements and those of Modula-2. But the user
can, through the use of an environment variable (M2OUTPUT), specify
that standard OBJ files are to be generated instead.

The Compiler 14

4.1 Running the integrated compiler: MC

Compiler invocation:

MC [workModule] [/p mainModule] [/s maxIds idSpace] [/c] [/e]
[/m] [/d-]

The '/p' option may be used to indicate the name of the main module of
the program that you are working on (the name should not have an
extension). If this option is not used, but workModule is entered
without an extension, the same name is also used for mainModule.

The '/s' option allows you to change the default sizes of the compiler
identifier tables. The two arguments specify the maximum number of
different identifiers to be processed, and the total string space to
be allocated to store these identifiers. The default values are 2000
and 12000, respectively.

If you use of the '/c' command line option, the compiler starts
compiling "workModule" immediately and, if no errors are encountered,
will bring you right back to the DOS prompt. This is useful when
running the compiler from a batch file:

MC myprog /c

The '/e' option will send you straight into the editor.

The '/m' option invokes the make processor, which will look for the
file mainModule.MAK for the dependencies list.

The '/d-' option sets the default value of the compiler directives $R
and $T to '-', disabling the default generation of most runtime error
checking. We do not recommend disabling the stack overflow checking,
and the use of '/d-' will not do it.

The compiler always sets the DOS errorlevel to 0 if the last compile
was successful (no errors); otherwise, the DOS errorlevel is set to 1.

If the compiler is invoked without the '/c', '/e' or '/m' options, you
will get a screen that looks something like this:

The Compiler 15

Modula-2 compiler, Version 2.0
(C) Copyright 1987,1988 Fitted Software Tools.
All rights reserved.

Memory model in use: LARGE
Output file format: M2O

Heap in use: 0K
Available Heap: 249K

Program: sieve

Work module: sieve.MOD

Program New Options DOS Quit dbg2map
Compile Edit Genmake Make Link eXecute >

The options at this point are:

Program Specify the name of the main program module.

New Specify another "Work module".

Options To select the memory model to use.

DOS Invoke a new DOS shell. At the DOS prompt, you
should type EXIT to return to this system.

Quit Return to DOS.

dbg2map (2) Execute DBG2MAP, passing as argument the name in

Compile Compile the "Work module".

Edit Edit the "Work module".

Genmake Invoke the GenMake program, passing as argument the
name in Program -- and '/OBJ', if appropriate.

Make Recompile all the necessary modules as per the rules
of a makefile (The makefile is assumed to have the
name in Program and the extension of .MAK). Note: If
errors are encountered during the compilation of one
of the modules, the make process is aborted. After
fixing the errors, select Make again.

Link Invokes the linker (M2Link) passing along as

The Compiler 16

arguments the name in Program and '/L'.

eXecute Program is executed.

4.2 Running the freestanding compiler: M2COMP

Compiler invocation:

M2COMP filename [/m] [/s maxIds idSpace] [/d-]

filename is the name of the module to compile or, if the /M option is
used, the name of the makefile to process.

The DOS errorexit is set to 0 if the compilation (make) is successful
and to 1 otherwise.

4.3 The compilation process The input file

If the module to be compiled is already loaded into one of the editor
buffers, that source is compiled. Otherwise, the compiler tries to
open the named file. The imported modules

The compiler and the linker cooperate in assuring that all the modules
that refer to a particular definition module will have been compiled
against the same version of that definition module.

To this end, the compiler places in the 'module header' and 'module
import' records of the object file a "module key". This module key is
the date of the DEF file used during the compilation of the
implementation module or during the processing of the IMPORT

The Compiler 17

Due to this, the compiler will not look in the editor buffers for the
DEF files needed to process an IMPORT list. These are always read in
from the disk. The output file

The output from the compilation of a main module or an implementation
module is a single output file, with the same name of the source file
but with the extension of 'M2O' (Modula-2 Object) -- OBJ files are
created instead, if the environment variable M2OUTPUT so specifies.

The compilation of a definition module does not generate any new
output files. If the compilation is successful (no errors), the
compiler simply 'touches' the source file, updating its modification
time. A warning

Because of the fact that the compiler uses the date of the DEF file as
that module's key, you may not modify a DEF file unless you intend to
recompile all the modules that use it, nor can you copy the file in
such a way that its date is not preserved.

In particular, if you are going to be transferring your modules
between computers, you must use some procedure that will preserve all
the DEF files' dates.

This is probably a good place to point out that, when you use OBJ
files, you are not protected by this module version checking.

4.4 Compiler directives

Certain compiler code generation options may be set through directives
included in the program text. These directives must appear
immediately at the beginning of a comment; multiple directives may be
entered in a single comment by separating them by commas. Example

(* $S-, $R+ *)

A '+' sets the directive to TRUE, a '-' sets it to FALSE, and a '='

The Compiler 18

pops the directive's value prior to the last '+' or '-'.

The following compiler directives are defined:

$A Alignment. Default $A+. If enabled, all new variables
declared are aligned on a word boundary. Record
fields are packed (not aligned) regardless of the
setting of this option.

$S Stack overflow checking. Default $S+. If enabled,
stack overflow checking is performed on entry to a
procedure and when copying open arrays to a
procedure's local stack frame.

$R Range checking. Default $R+. If enabled, before any
assignment is made to a variable of a subrange type,
the value to be assigned is tested against the limits
of the subrange type.

$T Array subscript and NIL pointer checking. Default
$T+. If enabled, any time a subscript operation is
performed on an array, the subscript value is checked
to confirm that the operation would not generate an
address outside the bounds of the array. In
addition, before a pointer is dereferenced, its value
is checked for NIL.

$L Generate line number information. Default $L-. If
this option is enabled, the compiler will include a
list of source code line numbers and their
corresponding object code offsets in the output
file. This line number information is passed on to
the .DBG file when the program is linked with the /L
option. Benchmarks

If you are going to benchmark the code generated by this compiler,
please disable the generation of runtime error checking on all the
compilers involved in the comparison.

We feel compelled to spell this out because some other vendors'
products do not generate runtime error checking by default.

4.5 Runtime errors

The Compiler 19

When, during the execution of a program, a runtime error is detected,
the runtime error handler will terminate the program and write out a
message indicating the type of error encountered and its location (PC

To find the location of the error in the source code, run DBG2MAP
against the .DBG file generated by M2LINK for this program. Scanning
the .MAP file created, you should be able to always determine the
module and procedure where the error occured. If the $L+ directive
was used when compiling the module in question and the /L option was
used when linking the program, the error location can be pinpointed to
the offending line by scanning the line number information at the end
of the .MAP file.

4.5.1 Trapping runtime errors in your program

The Library module System provides you with a means of intercepting
runtime errors. The following are the currently defined runtime error
numbers that may be passed to your error handler routine:

0 stack overflow ($S option)
1 range error ($R or $T option)
2 integer/cardinal overflow (divide by zero)
3 floating point error
4 function did not execute a RETURN
5 HALT was invoked

4.6 Compiler size limits

The following are the code and data size limits imposed by this

- A string constant cannot exceed 80 characters. This is also the
limit set for the size of any identifier.

- When using the HUGE memory model, each compilation module is
assigned its own data segment, which can be up to 64k in size.
In the data segment, the compiler allocates the space for all the
module's global variables and some of the module's constants.

- When using the LARGE memory model, all the modules' data are
combined, at link time, into a single data segment (64k


The Compiler 20

- The maximum size of a data structure is 65532 bytes.

- The maximum amount of space allocated for variables local to a
procedure is 32000 bytes.

- The compiler will also refuse to generate the code to pass, in a
procedure call, by value, a parameter greater than 65000 bytes in

The following are the compiler's internal limits:

- The maximum number of different (namewise) identifiers that can
be processed in a single compilation is 2000. May be overwritten
at compiler invocation.

- The total number of characters in all the different (namewise)
identifiers processed cannot exceed 12000 characters. May be
overwritten at compiler invocation.

- No single procedure can be translated into more than 10k of
object code.

- An array of 8k bytes is used to keep track of all the initialized
data for a module. This imposes a limit on the total amount of
string, real and long constants used in the compilation module.

4.7 The language supported

This release of the compiler will translate a program written in the
Modula-2 language as defined by Niklaus Wirth in the 3rd edition of
his book "Programming in Modula-2", with the exceptions noted bellow:

- Integer and Cardinal arithmetic overflow is not detected.

- ASM is a reserved word in this implementation.

- For those programmers that "grew up" in the Hex world, a way to
define CHAR literals in Hex is provided: 20X corresponds to the
"space" character in ASCII.


This compiler implements the standard types LONGINT and LONGCARD.

The Compiler 21

Operands of the type LONGINT or LONGCARD may appear in any expression,
just like INTEGER or CARDINAL. But that is about it!

Subranges of these types are not supported.

No standard procedure, except INC, DEC and the ones listed later in
this document will accept operands of one of these types.

A variable of type LONGINT or LONGCARD cannot be used as the control
variable in a FOR loop. Neither can CASE labels be of a LONG type.

Constants of type LONGINT or LONGCARD can be coded in decimal only and
must be terminated by an 'L' if the value is less than 65536. Example

123L and 123567 are valid LONGCARD or LONGINT constant

-1L and -348762 are valid LONGINT constants


The standard type LONGREAL is implemented.

The rules for the use of LONGREALs are the same as for REALs.

The types REAL and LONGREAL are not compatible, and no automatic
conversion from one type to another is ever performed -- the standard
procedures SHORT and LONG should be used to convert between these

Constants of type LONGREAL are no different from REAL constants. The
type of the constant is determined by context. You may, however,
"type" a constant by the use of the SHORT or LONG procedure. Ex:

CONST longreal1 = LONG(1.0);

4.7.3 Additional or augmented standard procedures NEW and DISPOSE

NEW and DISPOSE have been deleted from the language definition in the
3rd edition of Wirth's book. We implement them thus:


Invokes the procedure ALLOCATE, which must conform to the type:


passing along p and the size of the object p is defined as pointing

The Compiler 22


Invokes the procedure DEALLOCATE, which must conform to the type:


passing along p and the size of the object p is defined as pointing

The procedures ALLOCATE and DISPOSE must, therefore, be defined in the
module using NEW and/or DISPOSE, or imported from some other module,
like Storage. LONG and SHORT







LONG takes an INTEGER, CARDINAL or REAL and converts it into a LONGINT
LONGCARD or LONGREAL, respectively.

SHORT takes a LONGINT, LONGCARD or LONGREAL and converts it into an

With our two integer/cardinal and real sizes, here is the behavior of
the TRUNC and FLOAT procedures.





The Compiler 23

4.8 Objects exported by the pseudo module SYSTEM TYPE BYTE

Takes 1 byte of storage. Only assignment is defined for this type.
If the formal parameter of a procedure is of type BYTE, the
corresponding actual parameter may be of any type that takes 1 byte of

If the formal parameter of a procedure is of type ARRAY OF BYTE, the
corresponding actual parameter may be of any type. TYPE WORD

Takes 1 word (2 bytes) of storage. Only assignment is defined for
this type. If the formal parameter of a procedure is of type WORD,
the corresponding actual parameter may be of any type that takes 1
word of storage.

If the formal parameter of a procedure is of type ARRAY OF WORD, the
corresponding actual parameter may be of any type. Care should be
taken in this case, as the size of the parameter passed is rounded up
to an even size. TYPE ADDRESS

The type ADDRESS is compatible with all pointer types. ADDRESS itself
is defined as a POINTER TO WORD. In this implementation, the type
ADDRESS is not compatible with any arithmetic type. This is due to
the fact that the Intel 8086 series processors use segmented
addresses. It would not be hard to implement automatic conversions
between LONGCARD and ADDRESS but it is felt that this would be
contrary to the spirit of the language, whereby the compiler is not
expected to perform any "magic" tricks. Instead, two functions are
provided for that purpose: FLAT and PTR.

In release 1.2 we relaxed the above a little. ADDRESS + CARDINAL and
ADDRESS - CARDINAL are legal expressions. The CARDINAL is added or
subtracted from the offset portion of the ADDRESS and the result is
still an ADDRESS.

Also, INC and DEC can take an ADDRESS as their first argument. The
operation is, however, performed on the offset portion of the ADDRESS

The Compiler 24 SEG and OFS

These are field definitions for POINTER types. If you import these,
you may access the segment or offset portions of a pointer variable
using regular field selection syntax. Example

pointer.SEG :segment portion of pointer PROCEDURE ADR

ADR( designator ) Returns the address of designator (type ADDRESS). PROCEDURE FLAT

FLAT( ADDRESS ) returns a LONGCARD "flat" address. PROCEDURE PTR

PTR( LONGCARD ) returns an ADDRESS corresponding to the "flat" address

SEGMENT( designator ) returns the segment portion of the address of
'designator'. Example:

DX := SEGMENT( buffer ); would assign to DX the segment value of

OFFSET( designator ) returns the offset portion of the address of


creates a new process whose entry point is p and workspace is at a for
n bytes. p1 is the new process pointer. This process is not
activated until a TRANSFER to p1 is done.

The starting priority of the new process is the current processor
priority at the time NEWPROCESS is invoked (please refer to the

The Compiler 25

section on Module Priorities). PROCEDURE TRANSFER


suspends the current process, assigning it to p1 and resumes p2. The
current process' value is assigned to p1 only after p2 has been
identified; it is, therefore, okay for p1 and p2 to be the same.

The process is resumed at the same priority level that it was running
at, at the time of suspension. PROCEDURE IOTRANSFER


issues a TRANSFER from p1 to p2 (just the way TRANSFER does it) after
installing the current process for reactivation when an interrupt
comes in through interrupt vector intVector.

When the interrupt occurs, the interrupt vector is reloaded with its
previous value. A TRANSFER is done to the I/O process (the one that
issued the IOTRANSFER) such that p2 now contains the value of the
process that was running when the interrupt occured. ASSEMBLER

An 8086 inline assembler is provided. Once ASSEMBLER is imported from
SYSTEM, you can enter inline assembler code by bracketing it with the
keywords ASM and END.

Assembler input is free form. Comments are entered as in regular
Modula-2. Example

loop: CMP BYTE [SI], 0 (*end of string?*)
INC SI INC DI (*increment pointers*)
JMP loop

The assembler accepts all the 8086/8088 opcode mnemonics. Address
operands can be coded in just about any form acceptable to other
assemblers, except that the only operator supported if '+'. Operand
type overrides are: WORD, BYTE, FAR, NEAR and are not to be followed
by the keyword POINTER or PTR. Example

label: MOV AX, ES:[BX,DI+5]
MOV WORD [5], 1

The Compiler 26

TEST BYTE i+2, 1

All the mnemonics and register names must be entered in upper case.
In case you need to use a Modula-2 name that conflicts with one of the
assembler reserved symbols, you may precede it with a '@'. Example


would generate a move from register AX to variable AX.

All modula-2 variables can generaly be accessed in assembler. Record
field names are not accessible from assembler. The assembler will not
automatically do anything for you. For example: if you specify a VAR
parameter as an operand to an instruction, you are naming the address
of the pointer to the actual parameter. Example

LES DI, done

is the correct way of storing TRUE in done.

The following types of constants may be accessed in assembler:
INTEGER, CARDINAL, BOOLEAN, CHAR and enumeration constants.

All labels declared inside an ASM section are local to that section of
code. But labels names cannot match some name known in the scope of
the current procedure. Labels can only be referenced in jump

All jumps are optimized by the compiler. There is, therefore, no need
(or capability) to specify the size of a jump. In particular, the
compiler will turn a conditional jump out of range into a reverse
conditional jump over a far jump to the original destination.

Remember, this is a Modula-2 compiler, not an assembler! The inline
assembler capability is provided for use in exceptional situations
only. ASSEMBLER - 8087 support

All the 8087 math coprocessor instructions are supported by the inline
assembler. There are some restrictions, however.

Only the following operand types are supported by the load and store
instructions: INTEGER, LONGINT, REAL and LONGREAL. You may not,
therefore, load or store a value in temporary real or decimal format.

The Compiler 27

The meaning of the "no operand" form of the arithmetic instructions
was retainned:

FADD, FSUB, FMUL and FDIV all operate on the two top elements of
the 8087 stack, using ST(1) as the destination and removing ST.

FSUBR subtracts ST(1) from ST (FDIVR divides ST by ST(1)),
leaving the result in ST(1) and removing ST.

The 2 operand format of the arithmetic instructions was not
implemented. You may not, therefore, specify a destination register
other than ST, except in the "and pop" versions of the instructions.

With a regular assembler, in register to register operations you can
specify the register that gets the result of the operation (the
destination register). By definition, the destination register is
also the first operand of the instruction.

With our inline assembler, ST is always the destination of the
operation, except in the "and pop" form of the instructions, in which
case the register specified in the instruction "gets the result".

For consistency, we decided that ST should always be the first operand
of the instruction, even when the "and pop" form is used.

The meaning of FSUBP, FSUBRP, FDIVP and FDIVRP is, therefore:

FSUBP ST(1) means FSUBRP ST(1),ST -> ST(1):=ST-ST(1)

FSUBRP ST(1) means FSUBP ST(1),ST -> ST(1):=ST(1)-ST

FDIVP ST(1) means FDIVRP ST(1),ST -> ST(1):=ST/ST(1)

FDIVRP ST(1) means FDIVP ST(1),ST -> ST(1):=ST(1)/ST

and ST is popped.

4.9 The generated object code

4.9.1 Data type representation

CHAR 1 byte

The Compiler 28

INTEGER 2 bytes 2's complement

CARDINAL 2 bytes

LONGCARD 4 bytes

LONGINT 4 bytes 2's complement

BOOLEAN 1 byte (1=TRUE, 0=FALSE)

REAL 4 bytes Intel 8087 format.

LONGREAL 8 bytes Intel 8087 format.

BITSET 1 word. 0 is low order bit, 15 is high order bit.

Enumerations 1 byte

SETs 1 to 8 words (sets of up to 256 elements)

POINTERs 4 bytes in Intel 8086/88 format

PROCEDUREs 4 bytes POINTER to procedure entry point

Addresses are represented in the default Intel 8086 format:

1 word byte offset

1 word segment

Numeric values are likewise represented the way the Intel 8086
processor family likes them: low order byte first, high order byte

4.9.2 The runtime memory map

Currently, the compiler generates code using the "large" or "huge"
memory model only.

In the "huge" memory model, each module has its own data and code

In the "large" memory model, each module has its own code segment.
The entire program has one data segment.

The linker binds all the code segments first, and then all the data
segments. The stack is allocated above the data segments. All the
remainning memory is available for the heap.

When a program is loaded for execution, here is what the memory looks

The Compiler 29


From low to high addresses:

0 ----------------------------------------------
I Interrupt vectors I
PSP I Program segment prefix I
PSP+100h I Program Code segments I
I Program Data segment(s) I
StackSeg I Stack I
HeapTop I Heap I
I ... I
I DOS Command (resident portion) I
MemTop ----------------------------------------------

Label names on the left are the ones exported by System.

This system uses interrupt vector 192 (0C0H) at location 0000:0300.
Interrupt 192 is issued by a program when a runtime error occurs, when
HALT is invoked or when a coroutine other than the main one terminates
via a return.

The first word (offset 0) in every code segment contains the data
segment value for that particular module (for the program, in the case
of the "large" memory model.

4.9.3 Procedure calling conventions

Procedure parameters are pushed into the stack 1st argument first.
Control is then transferred to the procedure through a FAR call. It
is the called procedure's responsibility to remove its parameters from
the stack before returning. Parameter passing (all except open array parameters)

If the formal parameter of a procedure is a value parameter, the
actual parameter is copied into the stack.

If the formal parameter is a variable parameter (VAR), the address of
the actual parameter is pushed into the stack (first the segment
portion of the address and then the offset part). Parameter passing (open array parameters)

The Compiler 30

If the formal parameter is an open array, the address and HIGH value
of the corresponding formal parameter are pushed into the stack (HIGH
value first, and then the address, as above).

If the open array parameter is a value parameter, the value of the
actual parameter is copied into the stack on procedure entry. Returning values from a function procedure

One byte results are returned in AL, two byte results are returned in
AX, and four byte results are returned in DX:AX (DX has the high order
part of the result).

LONGREALs are returned in the stack, at a location reserved for that
purpose by the caller. When invoking a function that returns a
LONGREAL, an extra parameter is pushed onto the stack: the two byte
offset, in the SS segment, of where to place the result. This choice
will make it easy to allow for the return of arbitrary structures from
a function, should the language standard go that way, while at the
same time allowing for full reentrancy of the code generated.

4.10 Module priorities

Eight module priority levels are supported in this implementation,
from 0 (highest priority) to 7 (lowest).

Priorities are implemented by masking off, on the 8259 interrupt
controller, all the interrupts at or below the current priority

Because the PC usually runs with several of the interrupt levels
disabled, it is not easy to decide what the interrupt mask for the
value for "no priority" should be for your particular application.
The implementation of NEWPROCESS, therefore, assumes that you have
enabled all the interrupts that your program will be capable of
processing before you create your processes. The value in the
interrupt mask register of the 8259 at the time of process creation
will determine the initial priority level of this process, once it
gets started. Because of this, invoking NEWPROCESS from inside a
priority module is usually not what you want to do!

Execution priorities are changed when entering/exitting procedures in
modules that have a priority specification, and during the execution
of some form of a TRANSFER.

The Compiler 31

We highly recommend that you study the communications program
provided, paying particular attention to the module Kernel, for an
example of how to use priorities with this system.

NOTE: The compiler does not restrict the priority level specified (any
number will do). You must, therefore, exercise care in defining a
module's priority level. On the other hand, it is easy to add
additional priority levels by simply modifying the runtime module

4.11 Memory models

In general, you may compile the same code under either the LARGE or
the HUGE memory model.

The only factor to consider is when using inline assembler.

Under the HUGE memory model, the compiler generates code to reload DS
after any invocation of an imported procedure or a VARiable
procedure. Under the LARGE memory model, this is not necessary as a
single data segment is defined. If you write some inline assembler
code that modifies DS, please restore it, even if the next thing you
do is a RETurn; this way, your routine will work regardless of whether
you use the LARGE or the HUGE memory model.

Under the HUGE memory model, access to external variables is done
through an indirect pointer, whereas in the LARGE memory model the
external variable resides in the program's ONLY data segment and is,
therefore directly accessible.

Using OBJ files 32

Chapter 5

Using OBJ files

As long as you use this system to write Modula-2 programs for the DOS
environment only, there is virtually no reason to use OBJ files. But,
in case you have to...

You condition the compiler to generate OBJ files by setting the
environment variable M2OUPUT to OBJ.


To link OBJ files you must exit the MC environment (or invoke the DOS
shell) and use some OBJ file linker.

Also, with OBJ files, there is no module version checking done for
you. Of course, if you keep your ".MAK" files up to date, you should
not encounter any problems.

5.1 GenLink

To help you figure out which files need to be linked, we provide a
utility (GenLink) that generates a LINK answer file. The LINK answer
file created by GenLink lists all the Modula-2 OBJ files that are
required to link your program.

Since your program, most likely, requires modules written in another
language (or you would not be using OBJ files, right?!), you will have
to edit the file created by GenLink to make it suitable.

5.2 Foreign Modules

Using OBJ files 33

To let the Modula-2 compiler know about modules written in other
languages, you must write FOREIGN DEFINITION modules. A foreign
definition modules is a regular definition module, with the exception
of the module's header, which goes like this:


where the 'C' or 'PASCAL' qualifier is optional.

5.2.1 External names

Names of public variables and procedures in foreign modules are
encoded in one of 3 ways:

In a regular FOREIGN (neither C nor PASCAL) module, the
identifiers are encoded in the object files as you enter them.

In a FOREIGN C module, identifiers are written out preceded by a
'_' character.

In a FOREIGN PASCAL module, identifiers are converted to all
upper case.

WARNING: As currently implemented, SET and STRING constants defined in
a FOREIGN DEFINITION module, cause the compiler to generate external
references to these. These "constants" should, therefore, be
allocated space and properly initialized in the foreign module.

5.2.2 Implementation

FOREIGN modules are not expected to have an initialization procedure,
and the compiler will not generate these initialization calls, as in
the case of regular Modula-2 modules. FOREIGN C modules

When invoking a routine defined in a FOREIGN C module, the arguments
are pushed onto the stack in reverse order, as per C's custom. Also,
the caller will remove the arguments off the stack upon return from
the subroutine.

Since C, unlike Modula-2, supports (?) the passing of a variable
number of arguments to a function, the symbol '...' may be used at the
end of a PROCEDURE parameter list definition to indicate that an

Using OBJ files 34

indeterminate number of arguments may be passed. Example:


defines a function that takes n integers and returns their sum. It
could, actually, be implemented in Modula-2 thus:

res := 0;
p := ADR(n) + 2;
WHILE n > 0 DO
res := res + p^;
INC( p, 2 );
DEC( n );
END sum;

Good luck!

In addition to being useful to define functions that take a variable
number of parameters, the use of '...' is also a handy (?!) way of
improving the odds that the arguments are passed in a form that C will
like. Parameter passing

The form in which the individual parameters are passed is always the
same, regardless of whether the procedure is in a foreign module or
not. The exception is when you use '...'.

When passing parameters that correspond to the '...' in the procedure
heading, the compiler follows the default C rules: Everything is
passed by value, except for arrays, which are passed by reference
(their address, instead of their value, is pushed onto the stack).

Modula-2 does not allow functions to return structured types. Some C
compilers return structured values by actually returning a pointer to
those values in the DX:AX register pair, which is just the way that
Fitted Modula-2 returns pointers! With these, therefore, you could

struct someStruct cfunct()


TYPE someStructPtr = POINTER TO someStruct;

Using OBJ files 35

PROCEDURE cfunct() :someStructPointer;

5.2.3 In the real world...

Knowing the parameter passing conventions used by the compiler you
should have no trouble writing assembly language modules to be invoked
by Modula-2.

With the help provided (FOREIGN C and '...'), it should be easy enough
to interface Modula-2 to C. But is it, really? Not quite!

There are two main problems that you will have to overcome. One, is
the choice of a suitable memory model. Our LARGE memory model is
probably a better choice than HUGE, as some compilers require DS to
always point to DGROUP.

The other problem, is the set of requirements imposed by each
language's runtime system. Since we provide all the source code for
our runtime, your best bet will probably be to modify our system to
suit theirs. Modules that are obvious candidates for "adaptation" are
System and Storage; In their current state, they are virtually
guarateed to not work with another vendor's runtime system, and they
are a basis on which many other library modules depend.

The Text Editor 36

Chapter 6

The Text Editor

The text editor included in this package has all the features that you
have come to expect from a basic program editor: the ability to
insert, delete, move, find and replace text; support for concurrent
editing of multiple files (as many as will fit in memory) in separate
windows (as many as will fit on the screen) with the ability to copy
or move text from window to window.

Although you may load the same file in two different windows, the
editor will not be aware of the fact and will treat the two copies as
two different files.

The only preset limitation in the editor is that it cannot handle
files bigger than 64k. This decision was justified by the fact that
Modula-2 programs are supposed to be modular. File load/save speed
was the overriding factor here.

All the text editor keys are defined by the user through the use of
the EDCONFIG program. When the editor starts, it expects to find the
file M2ED.CFG in the current PATH.

M2ED.CFG will also tell the editor what display colors (attributes) to
use for the Status line, for Normal text and for Marked text blocks.

Finally, M2ED.CFG also contains the default settings for the TAB size
value, as well as whether or not the editor will expand the tabs
inserted into the text spaces. Note: Tabs present in a file will not
be expanded to spaces by the editor.

To get you started, we provide a M2ED.CFG file with the following

Cursor left : Left
Cursor right : Right
Cursor up : Up
Cursor down : Down
Previous word : ^Left
Next word : ^Righ
Page up : PgUp
Page down : PgDn
Cursor to beginning of line : Home
Cursor to end of line : End

The Text Editor 37

Cursor to top of window : ^Home
Cursor to bottom of window : ^End
To beginning of file : ^PgUp
To end of file : ^PgDn
Current line to top of window : AltT
Toggle insert/overtype : Ins
Delete character under cursor : Del
Delete previous character : ^H
Delete Current Line : ^Y
Delete to EOL : AltY
Delete Word : ^D
Indent Line : F4
Unindent Line : F3
Indent Block : Alt=
Unindent Block : Alt-
New file : AltN
Read file : AltR
Write block : AltW
Save file : AltS
Open window : ^O
Close Window : ^C
Next window : F2
Previous window : aF2
Split screen : ^S
Mark beginning of block : F7
Mark end of block : F8
Goto beginning of block : AltB
Goto end of block : AltE
Clear block marks : AltH
Copy block : AltC
Delete block : AltD
Move block : AltM
Search forward : F5
Search backwards : aF5
Replace forward : F6
Replace backwards : aF6
Global replace : ^F6
Repeat last search/replace : F1
Goto next error : ^E
Goto previous error : ^P
Goto line : AltG
Set options : AltO
Redraw the screen : ^L
Quit : AltQ

The Linker 38

Chapter 7

The Linker

The linker is invoked by the command line

M2LINK myprog [/s n] [/h n] [/o] [/l] [/swap [path]]

where 'myprog' is the main module of the program you are creating.
The options are thus:

/s n n is the size of the stack to allocate (default is

/h n n is the amount of space to reserve for the heap (in
paragraphs). The default is all the free memory.

/o invokes the optimizer. The optimizer prevents the
output, to the object file, of all the procedures
that are part of included modules but are not
referenced. This will make your final EXE files

/l tells the linker to process the line number
information in the .M2O files and include it in the
.DBG file. This option is disabled if the optimizer
is invoked.

/k tells the linker to ignore module keys, i.e. to not
check for module version compatibility. This option
should be used with extreme care.

/swap [path] tells the linker to use a swap file. Code segments
will be kept in this swap file instead of in main
memory during the link process. This allows you to
link larger programs.

The linker creates two files: the .EXE file is your executable
program, the .DBG file is a file containning symbol information for
use by other utilities (see Map file generator, Profiler).

If the /swap directive is used, a swap file is created. You may
select the path (drive:directory) where the swap file is to be
created. Example:

The Linker 39

M2LINK myprog /swap D:

7.1 Module keys

The module header record and the import records written out by the
compiler to the object file are stamped with the date of the .DEF file
that was processed - this becomes the module key. The linker will
assure that these module keys in the module header of the imported
module and in the import record match; If they do not match, both
modules were not compiled using the same definition module.

Because of the use of module keys, it is imperative that the date of
the distributed .DEF files not be modified unless you intend to
recompile the implementation modules.

When using OBJ files, you do not have the protection of Module keys.

Other utilities 40

Chapter 8

Other utilities

8.1 Editor configurator

This program lets you define the keystrokes to be used to invoke all
the editor commands, the screen attributes (colors) to use, and the
default editor options.



EdConfig presents you with a menu from which you may elect to modify
the default editor options, the display attributes, or configure the
editor commands.

If you are creating a new configuration file, you must configure the
editor commands.

If you chose to configure the editor commands, you will be prompted
for a log file (default M2ED.HLP), a text file in which all of your
command choices will be saved. You may print this file to create a
quick reference card. EDCONFIG will then prompt you for the key
sequence to be used for each editor command. For each command,
EDCONFIG will also give you the option of defining an alternate key

When you select Quit, the program will prompt you for an output file,
the default being 'M2ED.CFG'.

8.2 Map file generator

Other utilities 41


DBG2MAP program_name

Reads the .DBG file created by M2LINK and creates a DOS LINK
compatible .MAP file.

8.3 Make and the Makefile generator

These utilities eliminate the burden, on the user's part, of having to
figure out which modules are affected and, therefore, need to be
recompiled as a result of any changes to particular definition

GENMAKE creates the .MAK file, the file with all the dependencies
(this is the hard part) whereas MAKE (built into the compiler) will
insure that these dependencies are observed when updating the object

GENMAKE Invokation:

GENMAKE main_module_name [/l] [/obj]

generates the .MAK file containning all the module dependencies for
the named program. It does this by reading all the IMPORT statements
in the main module and, recursively, generating the dependency lists
for all those modules. GENMAKE will indeed read all the .MOD and .DEF
files involved.

The /l option instructs GenMake to include the directories listed in
the environment variable M2LIB in its search path. Otherwise, only
the modules in the current directory will be taken into consideration
when creating the makefile.

The /obj option tells GenMake that you will be using the compiler to
generate OBJ files instead of M2O files.

MAKE invocation: see "Running the Compiler".

MAKE will invoke the compiler as needed to assure that all the
dependencies in the make file are observed. MAKE is dumb in that it
will just run through the makefile sequentially. It was GENMAKE's
responsibility to see that the dependencies are listed in a proper
sequence. Please keep this in mind if you should edit a makefile!

Other utilities 42

8.4 The execution profiler


M2Prof program_name

The profiler will ask you for the name of the .DBG file to use (if it
cannot find it) and give you an option of profiling your entire
program (generating an execution profile by module), a particular
module (generating an execution profile by procedure in that module)
or a particular procedure (generating an execution profile by line in
the procedure).

Upon program termination, the profiler outputs the list of all the
modules/procedures/lines profiled, ranked by execution time, to a file
of your choice.

This profiler is not that versatile, but it is useful nevertheless.
It proved instrumental in pinpointing some obvious areas for
improvement in the compiler (Oh, we did not tell you, did we? This
compiler was written in the language it compiles -- Modula-2 -- and
this system was used as our primary development tool since very early
in the development process).

The Library Modules 43

Chapter 9

The Library Modules

For complete information on what each library module provides, as well
as its proper usage, please refer to the .DEF files.

In addition, the source code of all the library modules is available
to all the registered users (see the order form in the back of this
document for details).

9.1 Release 2.0 libraries

In this release, several library modules were "extended". We have not
created any source level incompatibility with previous library
modules, that we are aware of. But you will have to recompile all
your programs, as they will not link with the new library modules.

If you customized any of the ASM modules, please note that their
format was slightly changed and a module initialization routine is now

The runtime support system 44

Chapter 10

The runtime support system

The library module System contains the runtime system's initialization
code. In particular, special interrupt vectors are loaded with the
addresses of routines (also in System) that will handle runtime errors
and other abnormal program terminations. In addition, the module
Storage depends on System doing its stuff -- setting the HeapBase,
HeapTop and MemTop variables.

Three other special modules are included in this package. M2Reals,
M2Longs and M2Procs. These modules provide support for specific
language features.

M2Reals handles all the REAL and LONGREAL arithmetic and conversions.
In release 2, M2Reals checks for the presence of an 8087 math
co-processor and uses it, if found.

M2Longs handles LONGINT and LONGCARD arithmetic.

M2Procs provides the coroutine support.

Shareware 45

Chapter 11


This software package is distributed as Shareware.

If you try this program and continue to use it, you are expected to
register with us.

This software can be freely distributed, as long as no money is
charged for it, all the files are included, unmodified, and with their
modification dates preserved.

This software cannot be distributed as a part of, or in conjunction
with, another product.

This software cannot be used in a commercial environment without the
payment of a $29 (as of this writing) license fee per copy.

Our success will depend not only on the quality of this software but
on the willingness of every individual user to "support" its
developers. If you use this product, please send in the registration
form in the back of this document, along with your registration fee.
For a modest $49 (as of this writing), we will send you the latest
version of this software and all the library and runtime support
source code. This source code is made available to registered users

Whether or not you use this product, please give complete copies of
this software to others.

License terms 46

Chapter 12

License terms

Before you register this product and become a licensed user, you are
granted a limitted license to evaluate the product to determine
whether or not it will fit your needs. Use of this system for any
other purpose, before registration and without our written consent, is
expressly forbidden.

Registered users are given a non-exclusive license to use this
software on any machine that they have access to, but not on more than
one at a time (the "treat this software like a book" idea).

Registered users may modify the source code provided to suit their
needs, but this source code (in original or modified form) may not be
distributed without the prior written consent of Fitted Software

Registered users may include compiled portions of the library and
runtime support code in the programs by them developed, and use or
distribute these programs without payment of any additional license
fees to Fitted Software Tools.

Support 47

Chapter 13


Our basic philosophy is very simple: Without happy users, we do not
have a business -- or, at least, we will not have one for long!

We will do everything in our power to assure that our users get the
kind of support that they deserve and we can afford to provide.

Above all, we do not want to create false expectations on the part of
our users, the reason for this chapter.

We currently provide our registered users with support by mail,
through BIX (conference 'fst'), or through our BBS, at 214/517-4629.

We cannot, of course, promise to fix any bug that you may find within
a certain period of time. As a matter of fact, we do not even promise
to fix any and all bugs that you may find, but we will try... When a
fix is not imminent, we will try to give you a workaround procedure,
so that you may go on with your work.

As we fix bugs, we will make the new versions of the affected programs
available for download from the BBS. Should this not be acceptable to
you, you may elect to have the fixes mailed to you, for $5 to cover
media and handling charges.

We also make new product updates available for download off the BBS.

Registered users have the option of getting software updates by mail
instead of downloading them. The current price of such updates is

Your input matters to us 48

Chapter 14

Your input matters to us

You can bet that this is serious! We know, and you know, that there
are many ways in which this system can be improved. It is in our
common interest that we agree on just how (what needs changing, what
additional capabilities are needed) and when (let's take care of the
more important stuff first!).

Maybe you like this software so much that you would hate to see us
improve it in the wrong direction (ha, ha, ha)...

Maybe you find some weaknesses in this product that make it awkward to

Maybe even (God forbid!) that one or more of those weaknesses make
this software unusable for your purposes.

Whichever the case may be, we need to know about it, our future is at

So, please!, fill out the survey form and send it in.

Your comments would be appreciated

How did you first learn about this product?


Where did you get this software from?

( ) us ( ) a bulletin board
( ) a friend phone # ___ ___ ____
( ) a computer club ( ) a shareware software distributor
( ) other ________________________

Systems you intend to use this software on

( ) PC (8088/8086) ( ) AT (80286) ( ) 80386

Typical system's configuration

( ) hard disk
( ) 512k ( ) 640k
( ) extended memory
( ) expanded memory (EMS, EEMS)
( ) EGA adapter
( ) VGA adapter

What programming languages do you use regularly?


What do you like the most about this system?


What do you NOT like about this system?


Other comments / suggestions:


We would like to think that our software is bug free, but we have been
around a while.

So, if you uncover one of those nasty critters, please provide us with
the information below, and whatever else that may help us duplicate
the problem.




City, State, Zip_________________________________

Telephone _____________

Version of the software in use: ___________________________

Machine in use (make and model): ___________________________

Memory / Disks / Display type: ___________________________

Operating system used: ___________________________

Other system information that may be pertinent (PATH settings,
CONFIG.SYS contents,...)

Problem description:


Please mail this form to:

Fitted Software Tools
P.O.Box 867403
Plano, TX 75086

to register your copy/copies of the Modula-2 compiler, register/order
additional copies, and/or order updates.

The unauthorized distribution of the library and runtime support
source code included in the distribution disks that you receive when

you order a registered copy or update is specifically prohibited.

If you are ordering multiple copies for your organization (or for you
and your friends), we suggest that you order 1 of the $49 packages and
the rest as $29 registrations.




City, State, Zip_________________________________

___ X Registration & latest version @ $49.00 (*) _________

___ X Additional Registrations @ $29.00 _________

___ X Floppy updates @ $12.00 (**) _________

Sales tax (TX residents) _________

Total enclosed: _________

Disk format preferred (360k 5-1/4" is the default) ___________

If ordering the latest version, please specify how long you are
willing to wait for a new, if imminent, update ________________

Version of the software (the one displayed in the compiler screen)
that you are currently using __________

(*) We pay shipping.

(**) For updates outside the USA and Canada, please add an additional
$3.00 to help cover the additional shipping cost.

Table of Contents

Chapter 1 Introduction 2

1.1 Hardware requirements 3
1.2 Software requirements 3
1.3 For users upgrading to release 2 3

Chapter 2 Software installation 5

2.1 Theory 5
2.2 Recommended setup for a system with 2 floppy drives
2.3 Recommended setup for a hard disk system 7

Chapter 3 A little tour through the system 9

3.1 The tour 9

Chapter 4 The Compiler 13

4.1 Running the integrated compiler: MC 14
4.2 Running the freestanding compiler: M2COMP 16
4.3 The compilation process 16 The input file 16 The imported modules 16 The output file 17 A warning 17

4.4 Compiler directives 17 Benchmarks 18

4.5 Runtime errors 18

4.5.1 Trapping runtime errors in your program 19

4.6 Compiler size limits 19
4.7 The language supported 20

4.7.2 LONGREAL 21
4.7.3 Additional or augmented standard procedures 21 NEW and DISPOSE 21 LONG and SHORT 22 FLOAT and TRUNC 22


4.9 The generated object code 27

4.9.1 Data type representation 27
4.9.2 The runtime memory map 28
4.9.3 Procedure calling conventions 29 Parameter passing (all except open array
parameters) 29 Parameter passing (open array parameters)
29 Returning values from a function procedure

4.10 Module priorities 30
4.11 Memory models 31

Chapter 5 Using OBJ files 32

5.1 GenLink 32
5.2 Foreign Modules 32

5.2.1 External names 33
5.2.2 Implementation 33 FOREIGN C modules 33 Parameter passing 34

5.2.3 In the real world... 35

Chapter 6 The Text Editor 36

Chapter 7 The Linker 38

7.1 Module keys 39

Chapter 8 Other utilities 40

8.1 Editor configurator 40
8.2 Map file generator 40

8.3 Make and the Makefile generator 41
8.4 The execution profiler 42

Chapter 9 The Library Modules 43

9.1 Release 2.0 libraries 43

Chapter 10 The runtime support system 44

Chapter 11 Shareware 45

Chapter 12 License terms 46

Chapter 13 Support 47

Chapter 14 Your input matters to us 48

  3 Responses to “Category : Modula II Source Code
Archive   : M2DOC20.ZIP
Filename : FMODULA2.DOC

  1. Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!

  2. This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.

  3. But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: