FORTRAN v 3.31 - README File
8/30/85
This document presents product information that supercedes
or is not covered in the regular documentation. In
particular, this document covers product changes and
enhancements made immediately prior to release. It is
recommended that the user review the document immediately.
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Differences between version 3.31 and version 3.30
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A. Stack size of the compiler has been increased. By using
the included EXEMOD utility, you can specify the amount of
stack space to be available during compilation. If you
specify a bigger stack, you can compile larger programs,
but you will need more memory for the compiler to run.
The compiler comes initially configured with a 40K stack.
If the compiler does not run on your machine, because of
limited memory, you may wish to change the stack size to
some smaller amount. For many programs, a stack size of
10K proves to be ample. You can use EXEMOD to decrease
the stack size.
If the compiler fails with an "out of memory" error, the
stack is too small for the program you are attempting to
compile. You can use EXEMOD to increase the stack size.
B. A non-character expression can no longer be assigned to a
character variable. The following is no longer permitted:
REAL R
CHARACTER*5 C
C = R + 1.0
Direct assignments (not involving expressions) are permit-
ted:
REAL R
CHARACTER*5 C
C = R
C. The linker has been changed so that if it is directed to
combine code segments into a physical segment whose size
is within 36 bytes of the 64K limit, it will issue a warn-
ing message: "Segment longer than reliable size." This is
to protect against a bug in the Intel 80286 processor.
However, the message is only a warning. The executible
file will still be created. An attempt to build any seg-
ment, code or data, longer than 64K will still result in a
fatal error.
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Differences between version 3.30 and version 3.20
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A. The following sections have been modified or added to the
Microsoft FORTRAN User's Guide.
Update: Microsoft FORTRAN 3.3
Appendix A - Differences Between Versions 3.2 and 3.3
Appendix G - Mixed-Language Programming
Appendix H - Error Messages
Microsoft LIB - Library Manager Reference Manual
B. The following files are provided with the FORTRAN v 3.3
release, but are not completely documented in the User's
Guide. Whatever (additional) information is required to
use these files is provided in this document.
EXEPACK.EXE - Utility for packing .EXE files in order to
reduce their size and allow faster loading (refer to
subsection A.10 of the Microsoft FORTRAN User's Guide).
EXEMOD.EXE - Utility for viewing and modifying certain
header information in .EXE files (refer to subsection
A.10 of the Microsoft FORTRAN User's Guide).
CEXEC.LIB - Portion of Microsoft C library providing
routines to support the use of the MS-DOS 'exec'
function (function call 4B hex).
FOREXEC.INC - Interface declarations and documentation
for routines in CEXEC.LIB
DEMOEXEC.FOR - Example program demonstrating how to use
the routines provided in CEXEC.LIB.
EMOEM.ASM - Customization for the 8087.
DATTIM.FOR - Example demonstrating how to access the MS-
DOS date and time.
Please refer to the update notice at the beginning of the
User's Guide for a complete list of the files which have
been added to the FORTRAN v 3.3 release.
C. If your machine has an 8087 or an 80287, you should read
this closely to see if this pertains to your hardware
configuration. All Microsoft languages which support the
8087 need to intercept 8087 exceptions in order to
properly detect error conditions and provide reliable
accurate results. The math libraries which contain the
8087 exception handler and emulator (MATH.LIB and
8087.LIB) are designed to work without modification with
the following machines:
IBM PC family and compatibles, Wang PC
(any machine which uses NMI for 8087 exceptions)
Texas Instruments Professional Computer
There is a source file EMOEM.ASM included with the release
that can be modified. Any machine which sends the 8087
exception to an 8259 Priority Interrupt Controller (master
or master/slave) should be easily supported by a simple
table change to the EMOEM.ASM module. In the file there
are further instructions on how to modify the file and
patch libraries and executables.
If your computer is not listed, and you need to modify the
EMOEM.ASM program, please contact your hardware
manufacturer for the specific information on the 8087 and
what needs to be modified. If your hardware manufacturer
is not aware of the changes that need to be made they
should contact the Microsoft OEM Group.
Microsoft Retail Product Support is not equipped to help
out in the customization of the EMOEM.ASM program.
D. The library file, CEXEC.LIB, contains the following
routines extracted from the Microsoft C compiler library
(Version 3.0).
system - Invokes COMMAND.COM with a user-specified command
line.
spawn - Loads and executes a specified .COM or .EXE file
(i.e., executes a child process).
The file FOREXEC.INC contains INTERFACE declarations
allowing these routines to be called from FORTRAN and
extensive comments explaining how to use them.
The file DEMOEXEC.FOR contains an example program
demonstrating the use of these routines.
E. This section notes corrections to the documentation.
1. Microsoft FORTRAN User's Guide, page 144 (Appendix A -
Differences Versions 3.2 and 3.3):
The example program needs two additional lines to be
complete, as is shown below.
CHARACTER A*12, B*20, C*32
A='Now is the t'
B='ime for all good men'
C(1:12) = A
C(13:12+20) = B
write (*,*) 'C=',C
end
This will yield the output:
C=Now is the time for all good men
2. Microsoft FORTRAN User's Guide, page 143 (Appendix A -
Differences Between Versions 3.2 and 3.3):
In the character substrings description, the syntax for
arrays is shown as:
array (sub1, [,sub2])([first]:[last])
It should be:
array (sub1 [,sub2])([first]:[last])
the comma after "sub1" is incorrect, and should be
deleted.
3. Microsoft FORTRAN User's Guide, page 155 (Appendix A -
Differences Between Versions 3.2 and 3.3):
The first paragraph starts out:
"The memory allocation is pre-set to 6144 (6K) bytes."
This paragraph is actually referring to the stack size
and the 6K is incorrect. To verify the actual stack size
for the compiler passes, use the EXEMOD utility to
display the header fields of FOR1.EXE and PAS2.EXE.
4. Microsoft FORTRAN User's Guide - page 161 (Appendix A -
Differences Between Versions 3.2 and 3.3):
The segment contents for a FORTRAN program in memory are
listed below (from the highest memory location to the
lowest).
Heap - The "heap" is the area of the default data
segment (DGROUP) that is available for dynamic
allocation by the runtime support routines (e.g., for
file buffers). It does not belong to a named segment and
will not show up on a link map.
STACK - The STACK segment contains the user's stack,
which is used for function/subroutine calls and for
local, temporary variable storage in certain runtime
support routines.
_BSS - The _BSS segment contains all UNINITIALIZED
STATIC DATA (i.e., all uninitialized FORTRAN variables).
EEND, EDATA - Defined and used by the runtime library.
CONST - The CONST segment contains all CONSTANTS.
P3CE, P3C, P3CB, P2CE, P2C, P2CB, P1CE, P1C, P1CB, P3IE,
P3I, P3IB, P2IE, P2I, P2IB, P1IE, P1I, P1IB, XCE, XC,
XCB, XIE, XI, XIB - Defined and used by the runtime
library.
COMADS - Holds information needed to reference COMMON
blocks.
_DATA - The DATA segment is the default data segment.
All INITIALIZED GLOBAL AND STATIC data (i.e., all
initialized variables in FORTRAN) reside in this
segment.
NULL - The NULL segment is a special purpose segment
that occurs at the beginning of DGROUP. The NULL segment
contains the compiler copyright notice. This segment is
checked before and after the program executes. If the
contents of the NULL segment change in the course of
program execution, it means that the program has written
to this area. This will normally not occur in FORTRAN
but may arise if, for example, a C function is called
that uses an uninitialized pointer. The error message
"Null pointer assignment" is displayed to notify the
user.
__FBSS - Not used. Part of C runtime support.
Segments for COMMON and LARGE variables - Segments
allocated for COMMON blocks or LARGE variables will
normally occur here. However, this dependent on the link
order and they may occur above __FBSS if the
corresponding declarations do not occur in the first
.OBJ file in the link sequence.
C_ETEXT - The C_ETEXT segment marks the end of the code
segments. It contains no data and is therefore a segment
of zero length.
Code segments (listed as "module" in the illustration
on page 161) - Each module is allocated its own code
segment (also called a text segment). Code segments are
not combined, so there are multiple code segments.
However, all code segments have class CODE.
When implementing an assembly language routine to call
or be called from a FORTRAN program, you will probably
refer to the code and _DATA segments most frequently.
The code for the assembly language routine should be
placed in a user-defined segment with class CODE. Data
should be placed in whichever segment is appropriate to
their use, as described above. Usually this is the
default segment _DATA.
If linking with MS-C (3.0) routines, data segments,
outside of DGROUP, required for the C routines normally
occur between __FBSS and NULL. These segments will have
class name FAR_DATA or FAR_BSS depending on whether they
hold initialized C variables or uninitialized C
variables.
5. Microsoft FORTRAN User's Guide - page 164 (Appendix A -
Differences Between 3.2 and 3.3):
The following instructions in the entry and exit
sequences are NOT required:
inc bp
dec bp
The following instructions are included in order to
maintain compatibility with XENIX C, and therefore they
are OPTIONAL:
extrn __chkstk:far
call __chkstk
The following instructions are included in order to
maintain compatibility with MS-DOS C modules, and
therefore they are OPTIONAL:
push di
push si
pop di
pop si
6. Microsoft FORTRAN User's Guide, page 182 (Appendix F -
Exception Handling for 8087 Math):
It is not permitted to mask the invalid operation bit of
the 8087 control word.
7. Microsoft FORTRAN Reference Manual, page 107
(Statements):
Coercions from double to single precision are not
permitted in DATA statements. That is, if the variable
or array element in nlist is single precision then, the
corresponding value in clist cannot be double precision.
8. Microsoft FORTRAN Reference Manual, page 107
(Statements):
SEQUENTIAL=logical-sequential
DIRECT=logical-direct
FORMATTED=logical-formatted
UNFORMATTED=logical-unformatted
The stand-in variable names (logical-sequential etc)
should be changed to some other form such as
SEQUENTIAL=seqvar because these qualifiers yield
CHARACTER values, not LOGICAL ones.
9. Microsoft FORTRAN Reference Manual, page 186
(Metacommands):
The correct syntax for the $LARGE metacommand is as
follows.
$[NOT]LARGE[: name[, name]....]
Note that if the metacommand is given with arguments,
the colon (":") is required.
F. This section documents product features which are not
described in the User's Guide or Reference Manual.
1. Both the FORTRAN compiler and the runtime library
associate the name "ERR" with the MS-DOS standard error
device handle (generally abbreviated as stderr). Recall
that stderr is mapped to the physical console and,
unlike stdin and stdout, is not redirectable. Thus, the
command syntax:
FOR1 ERR;
will cause the FORTRAN compiler to expect source code
from the keyboard rather than a file named err.for.
Similarly, the command syntax:
FOR1 TEST,,ERR;
will cause the source listing output to written to the
console screen rather than a file named ERR.LST.
Finally, note that any OPEN statement, specifying "FILE
= 'ERR'", attaches the associated unit number to stderr,
hence to the physical console.
2. Both the compiler and the runtime use the Xenix
compatible I/O system in MS-DOS 2.xx/3.xx (MS-DOS 1.xx
is no longer supported). Thus, both the compiler and the
user's program will access files in other directories if
the proper pathnames are specified.
Since MS-DOS has a limit on the number of 'handles' that
may be simultaneously open for I/O, the user may
occasionally encounter an error 1034 ("too many open
files"). This may happen during execution of FOR1.EXE,
if there are nested include files. It may also occur at
runtime if the user tries to have too many files open at
the same time. In most cases, the problem is easily
circumvented using the "FILES = <number>" statement in
the CONFIG.SYS file (see your MS-DOS manual for
details). However, there is a fixed upper limit in MS-
DOS of 20 handles (five preassigned plus 15 others) that
any single program may have open simultaneously.
3. There have been several recent changes to the behavior
and capabilities of the EXEMOD and EXEPACK utilities
provided on this release which are not covered in the
printed manuals.
EXEPACK attempts to prevent you from compressing a file
onto itself. It is not infallible - it can be fooled by
a statement of the form:
EXEPACK TEST.EXE .\TEST.EXE
If it detects an attempt to compress a file onto itself
it will issue the message:
exepack: cannot pack file onto itself
and exit with return code 1. Also, when using EXEPACK
to compress an .EXE file with overlays, the compressed
file should be renamed back to the original name of the
linked file to avoid the overlay manager prompt (see
Overlays in the User Guide).
EXEMOD has an undocumented switch, /h, which can be seen
in the usage prompt (it is not shown in the Users Guide
description of the usage prompt). This option CANNOT be
used with any of the other options, and it is equivalent
to typing:
EXEMOD PROG.EXE
That is, it simply displays the header fields of the
.EXE file without modifying them.
EXEMOD has also been modified to work correctly on
packed (via EXEPACK) files. When it recognizes a packed
file, it will print the message:
exemod: (warning) packed file
If the stack value is changed, it modifies the value
that SP will have AFTER expansion. If either min or
stack is set, min will be corrected as necessary to
accomodate unpacking or stack. Setting max operates as
it would for unpacked files.
If the header of a packed file is displayed, the CS:IP
and SS:SP values are displayed as they will be after
expansion, which is not the same as the actual values in
the header.
The compiler executable files (FOR1, PAS2, and PAS3) are
not packed on the distribution diskettes. We recommend
that when you set up your own diskettes (as recommended
in the manual or otherwise), you run EXEPACK on all the
compiler executable files. You'll notice that the
savings is not great on most of them.
Note: Refer to the MS-DOS Programmer's Reference manual
for further information on .EXE file headers.
4. Controlling the Stack Size - the /STACK Linker option:
/STACK:number
The /STACK option allows you to specify the size of the
stack for your program. The number is any positive
value (decimal, octal, or hexadecimal) up to 65,536
(decimal). It represents the size, in bytes, of the
stack.
Note: The EXEMOD utility, can also be used to change the
default stack size.
G. The following public variables, defined in ENTX6L.ASM in
earlier versions of MS-FORTRAN, no longer exist in version
3.3.
BEGHQQ
BEGMQQ
CURHQQ
ENDHQQ
ENDMQQ
MAXMQQ
The following public variables, defined in ENTX6L.ASM in
earlier versions of MS-FORTRAN, still exist in version
3.30. Note, however, that only CESXQQ, CRCXQQ, CRDXQQ and
DOSEQQ are intended for direct access by the user.
CESXQQ - DOS saved ES value (for command line)
CLNEQQ - last line number encountered
CRCXQQ - value of CX for DOS call
CRDXQQ - value of DX for DOS call
CSXEQQ - pointer to sourcef context list
DGRMQQ - segment of DGROUP
DOSEQQ - DOS return code
HDRFQQ - Unit F open file list header
HDRVQQ - Unit V open file list header
PNUXQQ - pointer to unit initialization list
RECEQQ - machine error context, program segment
REFEQQ - machine error context, frame ptr
REPEQQ - machine error context, program offset
RESEQQ - machine error context, stack ptr
STKBQQ - stack start, to fix long GOTO
STKHQQ - stack limit, to check overflow
UPCX87 - offset address of 8087 error context
H. When reporting a suspected problem with the compiler to
the Retail Product Support Group, we ask that you please
provide the following information to help us in tracking
down the problem.
1. The smallest possible example which can be used to
demonstrate the alleged problem (the example should be
provided in source code, on a standard 5 1/4" MS-DOS
disk or a hard copy listing if it is very short).
2. A complete description of the symptoms of the problem
including complete directions on reproducing these
effects with the supplied example (compilation options
used, libraries linked with,...,etc.).
3. The compiler version number (from the logo that is
printed out when you run FOR1).
4. Your system configuration, both hardware (machine,
total memory, coprocessor,...,etc.) and software
(version of DOS, terminate-and-stay-resident utilities
or unusual system software, free memory as indicated by
chkdsk,...,etc.).
Having this information will be of immense help to us in
our effort to diagnose and solve your problem.
