This is g77.info, produced by makeinfo version 4.2 from g77.texi.

INFO-DIR-SECTION Programming
START-INFO-DIR-ENTRY
* g77: (g77).                  The GNU Fortran compiler.
END-INFO-DIR-ENTRY
   This file documents the use and the internals of the GNU Fortran
(`g77') compiler.  It corresponds to the GCC-3.1 version of `g77'.

   Published by the Free Software Foundation 59 Temple Place - Suite 330
Boston, MA 02111-1307 USA

   Copyright (C) 1995,1996,1997,1998,1999,2000,2001,2002 Free Software
Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "GNU General Public License" and "Funding Free
Software", the Front-Cover texts being (a) (see below), and with the
Back-Cover Texts being (b) (see below).  A copy of the license is
included in the section entitled "GNU Free Documentation License".

   (a) The FSF's Front-Cover Text is:

   A GNU Manual

   (b) The FSF's Back-Cover Text is:

   You have freedom to copy and modify this GNU Manual, like GNU
software.  Copies published by the Free Software Foundation raise
funds for GNU development.

   Contributed by James Craig Burley (<craig@jcb-sc.com>).  Inspired by
a first pass at translating `g77-0.5.16/f/DOC' that was contributed to
Craig by David Ronis (<ronis@onsager.chem.mcgill.ca>).


File: g77.info,  Node: Real Intrinsic,  Next: RealPart Intrinsic,  Prev: Range Intrinsic,  Up: Table of Intrinsic Functions

Real Intrinsic
..............

     Real(A)

Real: `REAL' function.  The exact type is `REAL(KIND=1)' when argument
A is any type other than `COMPLEX', or when it is `COMPLEX(KIND=1)'.
When A is any `COMPLEX' type other than `COMPLEX(KIND=1)', this
intrinsic is valid only when used as the argument to `REAL()', as
explained below.

A: `INTEGER', `REAL', or `COMPLEX'; scalar; INTENT(IN).

Intrinsic groups: (standard FORTRAN 77).

Description:

   Converts A to `REAL(KIND=1)'.

   Use of `REAL()' with a `COMPLEX' argument (other than
`COMPLEX(KIND=1)') is restricted to the following case:

     REAL(REAL(A))

This expression converts the real part of A to `REAL(KIND=1)'.

   *Note RealPart Intrinsic::, for information on a GNU Fortran
intrinsic that extracts the real part of an arbitrary `COMPLEX' value.

   *Note REAL() and AIMAG() of Complex::, for more information.


File: g77.info,  Node: RealPart Intrinsic,  Next: Rename Intrinsic (subroutine),  Prev: Real Intrinsic,  Up: Table of Intrinsic Functions

RealPart Intrinsic
..................

     RealPart(Z)

RealPart: `REAL' function, the `KIND=' value of the type being that of
argument Z.

Z: `COMPLEX'; scalar; INTENT(IN).

Intrinsic groups: `gnu'.

Description:

   The real part of Z is returned, without conversion.

   _Note:_ The way to do this in standard Fortran 90 is `REAL(Z)'.
However, when, for example, Z is `COMPLEX(KIND=2)', `REAL(Z)' means
something different for some compilers that are not true Fortran 90
compilers but offer some extensions standardized by Fortran 90 (such as
the `DOUBLE COMPLEX' type, also known as `COMPLEX(KIND=2)').

   The advantage of `REALPART()' is that, while not necessarily more or
less portable than `REAL()', it is more likely to cause a compiler that
doesn't support it to produce a diagnostic than generate incorrect code.

   *Note REAL() and AIMAG() of Complex::, for more information.


File: g77.info,  Node: Rename Intrinsic (subroutine),  Next: Repeat Intrinsic,  Prev: RealPart Intrinsic,  Up: Table of Intrinsic Functions

Rename Intrinsic (subroutine)
.............................

     CALL Rename(PATH1, PATH2, STATUS)

PATH1: `CHARACTER'; scalar; INTENT(IN).

PATH2: `CHARACTER'; scalar; INTENT(IN).

STATUS: `INTEGER(KIND=1)'; OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Renames the file PATH1 to PATH2.  A null character (`CHAR(0)') marks
the end of the names in PATH1 and PATH2--otherwise, trailing blanks in
PATH1 and PATH2 are ignored.  See `rename(2)'.  If the STATUS argument
is supplied, it contains 0 on success or a non-zero error code upon
return.

   Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine, or do not support the (optional)
STATUS argument.

   For information on other intrinsics with the same name: *Note Rename
Intrinsic (function)::.


File: g77.info,  Node: Repeat Intrinsic,  Next: Reshape Intrinsic,  Prev: Rename Intrinsic (subroutine),  Up: Table of Intrinsic Functions

Repeat Intrinsic
................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Repeat' to use this name for an
external procedure.


File: g77.info,  Node: Reshape Intrinsic,  Next: RRSpacing Intrinsic,  Prev: Repeat Intrinsic,  Up: Table of Intrinsic Functions

Reshape Intrinsic
.................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Reshape' to use this name for
an external procedure.


File: g77.info,  Node: RRSpacing Intrinsic,  Next: RShift Intrinsic,  Prev: Reshape Intrinsic,  Up: Table of Intrinsic Functions

RRSpacing Intrinsic
...................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL RRSpacing' to use this name
for an external procedure.


File: g77.info,  Node: RShift Intrinsic,  Next: Scale Intrinsic,  Prev: RRSpacing Intrinsic,  Up: Table of Intrinsic Functions

RShift Intrinsic
................

     RShift(I, SHIFT)

RShift: `INTEGER' function, the `KIND=' value of the type being that of
argument I.

I: `INTEGER'; scalar; INTENT(IN).

SHIFT: `INTEGER'; scalar; INTENT(IN).

Intrinsic groups: `f2c'.

Description:

   Returns I shifted to the right SHIFT bits.

   Although similar to the expression `I/(2**SHIFT)', there are
important differences.  For example, the sign of the result is
undefined.

   Currently this intrinsic is defined assuming the underlying
representation of I is as a two's-complement integer.  It is unclear at
this point whether that definition will apply when a different
representation is involved.

   *Note RShift Intrinsic::, for the inverse of this function.

   *Note IShft Intrinsic::, for information on a more widely available
right-shifting intrinsic that is also more precisely defined.


File: g77.info,  Node: Scale Intrinsic,  Next: Scan Intrinsic,  Prev: RShift Intrinsic,  Up: Table of Intrinsic Functions

Scale Intrinsic
...............

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Scale' to use this name for an
external procedure.


File: g77.info,  Node: Scan Intrinsic,  Next: Second Intrinsic (function),  Prev: Scale Intrinsic,  Up: Table of Intrinsic Functions

Scan Intrinsic
..............

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Scan' to use this name for an
external procedure.


File: g77.info,  Node: Second Intrinsic (function),  Next: Second Intrinsic (subroutine),  Prev: Scan Intrinsic,  Up: Table of Intrinsic Functions

Second Intrinsic (function)
...........................

     Second()

Second: `REAL(KIND=1)' function.

Intrinsic groups: `unix'.

Description:

   Returns the process's runtime in seconds--the same value as the UNIX
function `etime' returns.

   On some systems, the underlying timings are represented using types
with sufficiently small limits that overflows (wraparounds) are
possible, such as 32-bit types.  Therefore, the values returned by this
intrinsic might be, or become, negative, or numerically less than
previous values, during a single run of the compiled program.

   For information on other intrinsics with the same name: *Note Second
Intrinsic (subroutine)::.


File: g77.info,  Node: Second Intrinsic (subroutine),  Next: Selected_Int_Kind Intrinsic,  Prev: Second Intrinsic (function),  Up: Table of Intrinsic Functions

Second Intrinsic (subroutine)
.............................

     CALL Second(SECONDS)

SECONDS: `REAL'; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Returns the process's runtime in seconds in SECONDS--the same value
as the UNIX function `etime' returns.

   On some systems, the underlying timings are represented using types
with sufficiently small limits that overflows (wraparounds) are
possible, such as 32-bit types.  Therefore, the values returned by this
intrinsic might be, or become, negative, or numerically less than
previous values, during a single run of the compiled program.

   This routine is known from Cray Fortran.  *Note CPU_Time Intrinsic::,
for a standard equivalent.

   For information on other intrinsics with the same name: *Note Second
Intrinsic (function)::.


File: g77.info,  Node: Selected_Int_Kind Intrinsic,  Next: Selected_Real_Kind Intrinsic,  Prev: Second Intrinsic (subroutine),  Up: Table of Intrinsic Functions

Selected_Int_Kind Intrinsic
...........................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Selected_Int_Kind' to use this
name for an external procedure.


File: g77.info,  Node: Selected_Real_Kind Intrinsic,  Next: Set_Exponent Intrinsic,  Prev: Selected_Int_Kind Intrinsic,  Up: Table of Intrinsic Functions

Selected_Real_Kind Intrinsic
............................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Selected_Real_Kind' to use
this name for an external procedure.


File: g77.info,  Node: Set_Exponent Intrinsic,  Next: Shape Intrinsic,  Prev: Selected_Real_Kind Intrinsic,  Up: Table of Intrinsic Functions

Set_Exponent Intrinsic
......................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Set_Exponent' to use this name
for an external procedure.


File: g77.info,  Node: Shape Intrinsic,  Next: Short Intrinsic,  Prev: Set_Exponent Intrinsic,  Up: Table of Intrinsic Functions

Shape Intrinsic
...............

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Shape' to use this name for an
external procedure.


File: g77.info,  Node: Short Intrinsic,  Next: Sign Intrinsic,  Prev: Shape Intrinsic,  Up: Table of Intrinsic Functions

Short Intrinsic
...............

     Short(A)

Short: `INTEGER(KIND=6)' function.

A: `INTEGER'; scalar; INTENT(IN).

Intrinsic groups: `unix'.

Description:

   Returns A with the fractional portion of its magnitude truncated and
its sign preserved, converted to type `INTEGER(KIND=6)'.

   If A is type `COMPLEX', its real part is truncated and converted,
and its imaginary part is disgregarded.

   *Note Int Intrinsic::.

   The precise meaning of this intrinsic might change in a future
version of the GNU Fortran language, as more is learned about how it is
used.


File: g77.info,  Node: Sign Intrinsic,  Next: Signal Intrinsic (subroutine),  Prev: Short Intrinsic,  Up: Table of Intrinsic Functions

Sign Intrinsic
..............

     Sign(A, B)

Sign: `INTEGER' or `REAL' function, the exact type being the result of
cross-promoting the types of all the arguments.

A: `INTEGER' or `REAL'; scalar; INTENT(IN).

B: `INTEGER' or `REAL'; scalar; INTENT(IN).

Intrinsic groups: (standard FORTRAN 77).

Description:

   Returns `ABS(A)*S', where S is +1 if `B.GE.0', -1 otherwise.

   *Note Abs Intrinsic::, for the function that returns the magnitude
of a value.


File: g77.info,  Node: Signal Intrinsic (subroutine),  Next: Sin Intrinsic,  Prev: Sign Intrinsic,  Up: Table of Intrinsic Functions

Signal Intrinsic (subroutine)
.............................

     CALL Signal(NUMBER, HANDLER, STATUS)

NUMBER: `INTEGER'; scalar; INTENT(IN).

HANDLER: Signal handler (`INTEGER FUNCTION' or `SUBROUTINE') or
dummy/global `INTEGER(KIND=1)' scalar.

STATUS: `INTEGER(KIND=7)'; OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   If HANDLER is a an `EXTERNAL' routine, arranges for it to be invoked
with a single integer argument (of system-dependent length) when signal
NUMBER occurs.  If HANDLER is an integer, it can be used to turn off
handling of signal NUMBER or revert to its default action.  See
`signal(2)'.

   Note that HANDLER will be called using C conventions, so the value
of its argument in Fortran terms Fortran terms is obtained by applying
`%LOC()' (or LOC()) to it.

   The value returned by `signal(2)' is written to STATUS, if that
argument is supplied.  Otherwise the return value is ignored.

   Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine, or do not support the (optional)
STATUS argument.

   _Warning:_ Use of the `libf2c' run-time library function `signal_'
directly (such as via `EXTERNAL SIGNAL') requires use of the `%VAL()'
construct to pass an `INTEGER' value (such as `SIG_IGN' or `SIG_DFL')
for the HANDLER argument.

   However, while `CALL SIGNAL(SIGNUM, %VAL(SIG_IGN))' works when
`SIGNAL' is treated as an external procedure (and resolves, at link
time, to `libf2c''s `signal_' routine), this construct is not valid
when `SIGNAL' is recognized as the intrinsic of that name.

   Therefore, for maximum portability and reliability, code such
references to the `SIGNAL' facility as follows:

     INTRINSIC SIGNAL
     ...
     CALL SIGNAL(SIGNUM, SIG_IGN)

   `g77' will compile such a call correctly, while other compilers will
generally either do so as well or reject the `INTRINSIC SIGNAL'
statement via a diagnostic, allowing you to take appropriate action.

   For information on other intrinsics with the same name: *Note Signal
Intrinsic (function)::.


File: g77.info,  Node: Sin Intrinsic,  Next: SinH Intrinsic,  Prev: Signal Intrinsic (subroutine),  Up: Table of Intrinsic Functions

Sin Intrinsic
.............

     Sin(X)

Sin: `REAL' or `COMPLEX' function, the exact type being that of
argument X.

X: `REAL' or `COMPLEX'; scalar; INTENT(IN).

Intrinsic groups: (standard FORTRAN 77).

Description:

   Returns the sine of X, an angle measured in radians.

   *Note ASin Intrinsic::, for the inverse of this function.


File: g77.info,  Node: SinH Intrinsic,  Next: Sleep Intrinsic,  Prev: Sin Intrinsic,  Up: Table of Intrinsic Functions

SinH Intrinsic
..............

     SinH(X)

SinH: `REAL' function, the `KIND=' value of the type being that of
argument X.

X: `REAL'; scalar; INTENT(IN).

Intrinsic groups: (standard FORTRAN 77).

Description:

   Returns the hyperbolic sine of X.


File: g77.info,  Node: Sleep Intrinsic,  Next: Sngl Intrinsic,  Prev: SinH Intrinsic,  Up: Table of Intrinsic Functions

Sleep Intrinsic
...............

     CALL Sleep(SECONDS)

SECONDS: `INTEGER(KIND=1)'; scalar; INTENT(IN).

Intrinsic groups: `unix'.

Description:

   Causes the process to pause for SECONDS seconds.  See `sleep(2)'.


File: g77.info,  Node: Sngl Intrinsic,  Next: Spacing Intrinsic,  Prev: Sleep Intrinsic,  Up: Table of Intrinsic Functions

Sngl Intrinsic
..............

     Sngl(A)

Sngl: `REAL(KIND=1)' function.

A: `REAL(KIND=2)'; scalar; INTENT(IN).

Intrinsic groups: (standard FORTRAN 77).

Description:

   Archaic form of `REAL()' that is specific to one type for A.  *Note
Real Intrinsic::.


File: g77.info,  Node: Spacing Intrinsic,  Next: Spread Intrinsic,  Prev: Sngl Intrinsic,  Up: Table of Intrinsic Functions

Spacing Intrinsic
.................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Spacing' to use this name for
an external procedure.


File: g77.info,  Node: Spread Intrinsic,  Next: SqRt Intrinsic,  Prev: Spacing Intrinsic,  Up: Table of Intrinsic Functions

Spread Intrinsic
................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Spread' to use this name for an
external procedure.


File: g77.info,  Node: SqRt Intrinsic,  Next: SRand Intrinsic,  Prev: Spread Intrinsic,  Up: Table of Intrinsic Functions

SqRt Intrinsic
..............

     SqRt(X)

SqRt: `REAL' or `COMPLEX' function, the exact type being that of
argument X.

X: `REAL' or `COMPLEX'; scalar; INTENT(IN).

Intrinsic groups: (standard FORTRAN 77).

Description:

   Returns the square root of X, which must not be negative.

   To calculate and represent the square root of a negative number,
complex arithmetic must be used.  For example, `SQRT(COMPLEX(X))'.

   The inverse of this function is `SQRT(X) * SQRT(X)'.


File: g77.info,  Node: SRand Intrinsic,  Next: Stat Intrinsic (subroutine),  Prev: SqRt Intrinsic,  Up: Table of Intrinsic Functions

SRand Intrinsic
...............

     CALL SRand(SEED)

SEED: `INTEGER'; scalar; INTENT(IN).

Intrinsic groups: `unix'.

Description:

   Reinitialises the generator with the seed in SEED.  *Note IRand
Intrinsic::.  *Note Rand Intrinsic::.


File: g77.info,  Node: Stat Intrinsic (subroutine),  Next: Stat Intrinsic (function),  Prev: SRand Intrinsic,  Up: Table of Intrinsic Functions

Stat Intrinsic (subroutine)
...........................

     CALL Stat(FILE, SARRAY, STATUS)

FILE: `CHARACTER'; scalar; INTENT(IN).

SARRAY: `INTEGER(KIND=1)'; DIMENSION(13); INTENT(OUT).

STATUS: `INTEGER(KIND=1)'; OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Obtains data about the given file FILE and places them in the array
SARRAY.  A null character (`CHAR(0)') marks the end of the name in
FILE--otherwise, trailing blanks in FILE are ignored.  The values in
this array are extracted from the `stat' structure as returned by
`fstat(2)' q.v., as follows:

  1. Device ID

  2. Inode number

  3. File mode

  4. Number of links

  5. Owner's uid

  6. Owner's gid

  7. ID of device containing directory entry for file (0 if not
     available)

  8. File size (bytes)

  9. Last access time

 10. Last modification time

 11. Last file status change time

 12. Preferred I/O block size (-1 if not available)

 13. Number of blocks allocated (-1 if not available)

   Not all these elements are relevant on all systems.  If an element
is not relevant, it is returned as 0.

   If the STATUS argument is supplied, it contains 0 on success or a
non-zero error code upon return.

   Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine, or do not support the (optional)
STATUS argument.

   For information on other intrinsics with the same name: *Note Stat
Intrinsic (function)::.


File: g77.info,  Node: Stat Intrinsic (function),  Next: Sum Intrinsic,  Prev: Stat Intrinsic (subroutine),  Up: Table of Intrinsic Functions

Stat Intrinsic (function)
.........................

     Stat(FILE, SARRAY)

Stat: `INTEGER(KIND=1)' function.

FILE: `CHARACTER'; scalar; INTENT(IN).

SARRAY: `INTEGER(KIND=1)'; DIMENSION(13); INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Obtains data about the given file FILE and places them in the array
SARRAY.  A null character (`CHAR(0)') marks the end of the name in
FILE--otherwise, trailing blanks in FILE are ignored.  The values in
this array are extracted from the `stat' structure as returned by
`fstat(2)' q.v., as follows:

  1. Device ID

  2. Inode number

  3. File mode

  4. Number of links

  5. Owner's uid

  6. Owner's gid

  7. ID of device containing directory entry for file (0 if not
     available)

  8. File size (bytes)

  9. Last access time

 10. Last modification time

 11. Last file status change time

 12. Preferred I/O block size (-1 if not available)

 13. Number of blocks allocated (-1 if not available)

   Not all these elements are relevant on all systems.  If an element
is not relevant, it is returned as 0.

   Returns 0 on success or a non-zero error code.

   For information on other intrinsics with the same name: *Note Stat
Intrinsic (subroutine)::.


File: g77.info,  Node: Sum Intrinsic,  Next: SymLnk Intrinsic (subroutine),  Prev: Stat Intrinsic (function),  Up: Table of Intrinsic Functions

Sum Intrinsic
.............

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Sum' to use this name for an
external procedure.


File: g77.info,  Node: SymLnk Intrinsic (subroutine),  Next: System Intrinsic (subroutine),  Prev: Sum Intrinsic,  Up: Table of Intrinsic Functions

SymLnk Intrinsic (subroutine)
.............................

     CALL SymLnk(PATH1, PATH2, STATUS)

PATH1: `CHARACTER'; scalar; INTENT(IN).

PATH2: `CHARACTER'; scalar; INTENT(IN).

STATUS: `INTEGER(KIND=1)'; OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Makes a symbolic link from file PATH1 to PATH2.  A null character
(`CHAR(0)') marks the end of the names in PATH1 and PATH2--otherwise,
trailing blanks in PATH1 and PATH2 are ignored.  If the STATUS argument
is supplied, it contains 0 on success or a non-zero error code upon
return (`ENOSYS' if the system does not provide `symlink(2)').

   Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine, or do not support the (optional)
STATUS argument.

   For information on other intrinsics with the same name: *Note SymLnk
Intrinsic (function)::.


File: g77.info,  Node: System Intrinsic (subroutine),  Next: System_Clock Intrinsic,  Prev: SymLnk Intrinsic (subroutine),  Up: Table of Intrinsic Functions

System Intrinsic (subroutine)
.............................

     CALL System(COMMAND, STATUS)

COMMAND: `CHARACTER'; scalar; INTENT(IN).

STATUS: `INTEGER(KIND=1)'; OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Passes the command COMMAND to a shell (see `system(3)').  If
argument STATUS is present, it contains the value returned by
`system(3)', presumably 0 if the shell command succeeded.  Note that
which shell is used to invoke the command is system-dependent and
environment-dependent.

   Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine, or do not support the (optional)
STATUS argument.

   For information on other intrinsics with the same name: *Note System
Intrinsic (function)::.


File: g77.info,  Node: System_Clock Intrinsic,  Next: Tan Intrinsic,  Prev: System Intrinsic (subroutine),  Up: Table of Intrinsic Functions

System_Clock Intrinsic
......................

     CALL System_Clock(COUNT, RATE, MAX)

COUNT: `INTEGER(KIND=1)'; scalar; INTENT(OUT).

RATE: `INTEGER(KIND=1)'; OPTIONAL; scalar; INTENT(OUT).

MAX: `INTEGER(KIND=1)'; OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: `f90'.

Description:

   Returns in COUNT the current value of the system clock; this is the
value returned by the UNIX function `times(2)' in this implementation,
but isn't in general.  RATE is the number of clock ticks per second and
MAX is the maximum value this can take, which isn't very useful in this
implementation since it's just the maximum C `unsigned int' value.

   On some systems, the underlying timings are represented using types
with sufficiently small limits that overflows (wraparounds) are
possible, such as 32-bit types.  Therefore, the values returned by this
intrinsic might be, or become, negative, or numerically less than
previous values, during a single run of the compiled program.


File: g77.info,  Node: Tan Intrinsic,  Next: TanH Intrinsic,  Prev: System_Clock Intrinsic,  Up: Table of Intrinsic Functions

Tan Intrinsic
.............

     Tan(X)

Tan: `REAL' function, the `KIND=' value of the type being that of
argument X.

X: `REAL'; scalar; INTENT(IN).

Intrinsic groups: (standard FORTRAN 77).

Description:

   Returns the tangent of X, an angle measured in radians.

   *Note ATan Intrinsic::, for the inverse of this function.


File: g77.info,  Node: TanH Intrinsic,  Next: Time Intrinsic (UNIX),  Prev: Tan Intrinsic,  Up: Table of Intrinsic Functions

TanH Intrinsic
..............

     TanH(X)

TanH: `REAL' function, the `KIND=' value of the type being that of
argument X.

X: `REAL'; scalar; INTENT(IN).

Intrinsic groups: (standard FORTRAN 77).

Description:

   Returns the hyperbolic tangent of X.


File: g77.info,  Node: Time Intrinsic (UNIX),  Next: Time8 Intrinsic,  Prev: TanH Intrinsic,  Up: Table of Intrinsic Functions

Time Intrinsic (UNIX)
.....................

     Time()

Time: `INTEGER(KIND=1)' function.

Intrinsic groups: `unix'.

Description:

   Returns the current time encoded as an integer (in the manner of the
UNIX function `time(3)').  This value is suitable for passing to
`CTIME', `GMTIME', and `LTIME'.

   This intrinsic is not fully portable, such as to systems with 32-bit
`INTEGER' types but supporting times wider than 32 bits.  Therefore,
the values returned by this intrinsic might be, or become, negative, or
numerically less than previous values, during a single run of the
compiled program.

   *Note Time8 Intrinsic::, for information on a similar intrinsic that
might be portable to more GNU Fortran implementations, though to fewer
Fortran compilers.

   For information on other intrinsics with the same name: *Note Time
Intrinsic (VXT)::.


File: g77.info,  Node: Time8 Intrinsic,  Next: Tiny Intrinsic,  Prev: Time Intrinsic (UNIX),  Up: Table of Intrinsic Functions

Time8 Intrinsic
...............

     Time8()

Time8: `INTEGER(KIND=2)' function.

Intrinsic groups: `unix'.

Description:

   Returns the current time encoded as a long integer (in the manner of
the UNIX function `time(3)').  This value is suitable for passing to
`CTIME', `GMTIME', and `LTIME'.

   _Warning:_ this intrinsic does not increase the range of the timing
values over that returned by `time(3)'.  On a system with a 32-bit
`time(3)', `TIME8' will return a 32-bit value, even though converted to
an `INTEGER(KIND=2)' value.  That means overflows of the 32-bit value
can still occur.  Therefore, the values returned by this intrinsic
might be, or become, negative, or numerically less than previous values,
during a single run of the compiled program.

   No Fortran implementations other than GNU Fortran are known to
support this intrinsic at the time of this writing.  *Note Time
Intrinsic (UNIX)::, for information on a similar intrinsic that might
be portable to more Fortran compilers, though to fewer GNU Fortran
implementations.


File: g77.info,  Node: Tiny Intrinsic,  Next: Transfer Intrinsic,  Prev: Time8 Intrinsic,  Up: Table of Intrinsic Functions

Tiny Intrinsic
..............

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Tiny' to use this name for an
external procedure.


File: g77.info,  Node: Transfer Intrinsic,  Next: Transpose Intrinsic,  Prev: Tiny Intrinsic,  Up: Table of Intrinsic Functions

Transfer Intrinsic
..................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Transfer' to use this name for
an external procedure.


File: g77.info,  Node: Transpose Intrinsic,  Next: Trim Intrinsic,  Prev: Transfer Intrinsic,  Up: Table of Intrinsic Functions

Transpose Intrinsic
...................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Transpose' to use this name
for an external procedure.


File: g77.info,  Node: Trim Intrinsic,  Next: TtyNam Intrinsic (subroutine),  Prev: Transpose Intrinsic,  Up: Table of Intrinsic Functions

Trim Intrinsic
..............

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Trim' to use this name for an
external procedure.


File: g77.info,  Node: TtyNam Intrinsic (subroutine),  Next: TtyNam Intrinsic (function),  Prev: Trim Intrinsic,  Up: Table of Intrinsic Functions

TtyNam Intrinsic (subroutine)
.............................

     CALL TtyNam(UNIT, NAME)

UNIT: `INTEGER'; scalar; INTENT(IN).

NAME: `CHARACTER'; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Sets NAME to the name of the terminal device open on logical unit
UNIT or to a blank string if UNIT is not connected to a terminal.

   Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine.

   For information on other intrinsics with the same name: *Note TtyNam
Intrinsic (function)::.


File: g77.info,  Node: TtyNam Intrinsic (function),  Next: UBound Intrinsic,  Prev: TtyNam Intrinsic (subroutine),  Up: Table of Intrinsic Functions

TtyNam Intrinsic (function)
...........................

     TtyNam(UNIT)

TtyNam: `CHARACTER*(*)' function.

UNIT: `INTEGER'; scalar; INTENT(IN).

Intrinsic groups: `unix'.

Description:

   Returns the name of the terminal device open on logical unit UNIT or
a blank string if UNIT is not connected to a terminal.

   For information on other intrinsics with the same name: *Note TtyNam
Intrinsic (subroutine)::.


File: g77.info,  Node: UBound Intrinsic,  Next: UMask Intrinsic (subroutine),  Prev: TtyNam Intrinsic (function),  Up: Table of Intrinsic Functions

UBound Intrinsic
................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL UBound' to use this name for an
external procedure.


File: g77.info,  Node: UMask Intrinsic (subroutine),  Next: Unlink Intrinsic (subroutine),  Prev: UBound Intrinsic,  Up: Table of Intrinsic Functions

UMask Intrinsic (subroutine)
............................

     CALL UMask(MASK, OLD)

MASK: `INTEGER'; scalar; INTENT(IN).

OLD: `INTEGER(KIND=1)'; OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Sets the file creation mask to MASK and returns the old value in
argument OLD if it is supplied.  See `umask(2)'.

   Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine.

   For information on other intrinsics with the same name: *Note UMask
Intrinsic (function)::.


File: g77.info,  Node: Unlink Intrinsic (subroutine),  Next: Unpack Intrinsic,  Prev: UMask Intrinsic (subroutine),  Up: Table of Intrinsic Functions

Unlink Intrinsic (subroutine)
.............................

     CALL Unlink(FILE, STATUS)

FILE: `CHARACTER'; scalar; INTENT(IN).

STATUS: `INTEGER(KIND=1)'; OPTIONAL; scalar; INTENT(OUT).

Intrinsic groups: `unix'.

Description:

   Unlink the file FILE.  A null character (`CHAR(0)') marks the end of
the name in FILE--otherwise, trailing blanks in FILE are ignored.  If
the STATUS argument is supplied, it contains 0 on success or a non-zero
error code upon return.  See `unlink(2)'.

   Some non-GNU implementations of Fortran provide this intrinsic as
only a function, not as a subroutine, or do not support the (optional)
STATUS argument.

   For information on other intrinsics with the same name: *Note Unlink
Intrinsic (function)::.


File: g77.info,  Node: Unpack Intrinsic,  Next: Verify Intrinsic,  Prev: Unlink Intrinsic (subroutine),  Up: Table of Intrinsic Functions

Unpack Intrinsic
................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Unpack' to use this name for an
external procedure.


File: g77.info,  Node: Verify Intrinsic,  Next: XOr Intrinsic,  Prev: Unpack Intrinsic,  Up: Table of Intrinsic Functions

Verify Intrinsic
................

   This intrinsic is not yet implemented.  The name is, however,
reserved as an intrinsic.  Use `EXTERNAL Verify' to use this name for an
external procedure.


File: g77.info,  Node: XOr Intrinsic,  Next: ZAbs Intrinsic,  Prev: Verify Intrinsic,  Up: Table of Intrinsic Functions

XOr Intrinsic
.............

     XOr(I, J)

XOr: `INTEGER' or `LOGICAL' function, the exact type being the result
of cross-promoting the types of all the arguments.

I: `INTEGER' or `LOGICAL'; scalar; INTENT(IN).

J: `INTEGER' or `LOGICAL'; scalar; INTENT(IN).

Intrinsic groups: `f2c'.

Description:

   Returns value resulting from boolean exclusive-OR of pair of bits in
each of I and J.


File: g77.info,  Node: ZAbs Intrinsic,  Next: ZCos Intrinsic,  Prev: XOr Intrinsic,  Up: Table of Intrinsic Functions

ZAbs Intrinsic
..............

     ZAbs(A)

ZAbs: `REAL(KIND=2)' function.

A: `COMPLEX(KIND=2)'; scalar; INTENT(IN).

Intrinsic groups: `f2c'.

Description:

   Archaic form of `ABS()' that is specific to one type for A.  *Note
Abs Intrinsic::.


File: g77.info,  Node: ZCos Intrinsic,  Next: ZExp Intrinsic,  Prev: ZAbs Intrinsic,  Up: Table of Intrinsic Functions

ZCos Intrinsic
..............

     ZCos(X)

ZCos: `COMPLEX(KIND=2)' function.

X: `COMPLEX(KIND=2)'; scalar; INTENT(IN).

Intrinsic groups: `f2c'.

Description:

   Archaic form of `COS()' that is specific to one type for X.  *Note
Cos Intrinsic::.


File: g77.info,  Node: ZExp Intrinsic,  Next: ZLog Intrinsic,  Prev: ZCos Intrinsic,  Up: Table of Intrinsic Functions

ZExp Intrinsic
..............

     ZExp(X)

ZExp: `COMPLEX(KIND=2)' function.

X: `COMPLEX(KIND=2)'; scalar; INTENT(IN).

Intrinsic groups: `f2c'.

Description:

   Archaic form of `EXP()' that is specific to one type for X.  *Note
Exp Intrinsic::.


File: g77.info,  Node: ZLog Intrinsic,  Next: ZSin Intrinsic,  Prev: ZExp Intrinsic,  Up: Table of Intrinsic Functions

ZLog Intrinsic
..............

     ZLog(X)

ZLog: `COMPLEX(KIND=2)' function.

X: `COMPLEX(KIND=2)'; scalar; INTENT(IN).

Intrinsic groups: `f2c'.

Description:

   Archaic form of `LOG()' that is specific to one type for X.  *Note
Log Intrinsic::.


File: g77.info,  Node: ZSin Intrinsic,  Next: ZSqRt Intrinsic,  Prev: ZLog Intrinsic,  Up: Table of Intrinsic Functions

ZSin Intrinsic
..............

     ZSin(X)

ZSin: `COMPLEX(KIND=2)' function.

X: `COMPLEX(KIND=2)'; scalar; INTENT(IN).

Intrinsic groups: `f2c'.

Description:

   Archaic form of `SIN()' that is specific to one type for X.  *Note
Sin Intrinsic::.


File: g77.info,  Node: ZSqRt Intrinsic,  Prev: ZSin Intrinsic,  Up: Table of Intrinsic Functions

ZSqRt Intrinsic
...............

     ZSqRt(X)

ZSqRt: `COMPLEX(KIND=2)' function.

X: `COMPLEX(KIND=2)'; scalar; INTENT(IN).

Intrinsic groups: `f2c'.

Description:

   Archaic form of `SQRT()' that is specific to one type for X.  *Note
SqRt Intrinsic::.


File: g77.info,  Node: Scope and Classes of Names,  Next: I/O,  Prev: Functions and Subroutines,  Up: Language

Scope and Classes of Symbolic Names
===================================

   (The following information augments or overrides the information in
Chapter 18 of ANSI X3.9-1978 FORTRAN 77 in specifying the GNU Fortran
language.  Chapter 18 of that document otherwise serves as the basis
for the relevant aspects of GNU Fortran.)

* Menu:

* Underscores in Symbol Names::


File: g77.info,  Node: Underscores in Symbol Names,  Up: Scope and Classes of Names

Underscores in Symbol Names
---------------------------

   Underscores (`_') are accepted in symbol names after the first
character (which must be a letter).


File: g77.info,  Node: I/O,  Next: Fortran 90 Features,  Prev: Scope and Classes of Names,  Up: Language

I/O
===

   A dollar sign at the end of an output format specification suppresses
the newline at the end of the output.

   Edit descriptors in `FORMAT' statements may contain compile-time
`INTEGER' constant expressions in angle brackets, such as
     10    FORMAT (I<WIDTH>)

   The `OPEN' specifier `NAME=' is equivalent to `FILE='.

   These Fortran 90 features are supported:
   * The `O' and `Z' edit descriptors are supported for I/O of integers
     in octal and hexadecimal formats, respectively.

   * The `FILE=' specifier may be omitted in an `OPEN' statement if
     `STATUS='SCRATCH'' is supplied.  The `STATUS='REPLACE'' specifier
     is supported.


File: g77.info,  Node: Fortran 90 Features,  Prev: I/O,  Up: Language

Fortran 90 Features
===================

   For convenience this section collects a list (probably incomplete) of
the Fortran 90 features supported by the GNU Fortran language, even if
they are documented elsewhere.  *Note Characters, Lines, and Execution
Sequence: Characters Lines Sequence, for information on additional
fixed source form lexical issues.  Further, the free source form is
supported through the `-ffree-form' option.  Other Fortran 90 features
can be turned on by the `-ff90' option; see *Note Fortran 90::.  For
information on the Fortran 90 intrinsics available, see *Note Table of
Intrinsic Functions::.

Automatic arrays in procedures

Character assignments
     In character assignments, the variable being assigned may occur on
     the right hand side of the assignment.

Character strings
     Strings may have zero length and substrings of character constants
     are permitted.  Character constants may be enclosed in double
     quotes (`"') as well as single quotes.  *Note Character Type::.

Construct names
     (Symbolic tags on blocks.)  *Note Construct Names::.

`CYCLE' and `EXIT'
     *Note The `CYCLE' and `EXIT' Statements: CYCLE and EXIT.

`DOUBLE COMPLEX'
     *Note `DOUBLE COMPLEX' Statement: DOUBLE COMPLEX.

`DO WHILE'
     *Note DO WHILE::.

`END' decoration
     *Note Statements::.

`END DO'
     *Note END DO::.

`KIND'

`IMPLICIT NONE'

`INCLUDE' statements
     *Note INCLUDE::.

List-directed and namelist I/O on internal files

Binary, octal and hexadecimal constants
     These are supported more generally than required by Fortran 90.
     *Note Integer Type::.

`O' and `Z' edit descriptors

`NAMELIST'
     *Note NAMELIST::.

`OPEN' specifiers
     `STATUS='REPLACE'' is supported.  The `FILE=' specifier may be
     omitted in an `OPEN' statement if `STATUS='SCRATCH'' is supplied.

`FORMAT' edit descriptors
     The `Z' edit descriptor is supported.

Relational operators
     The operators `<', `<=', `==', `/=', `>' and `>=' may be used
     instead of `.LT.', `.LE.', `.EQ.', `.NE.', `.GT.' and `.GE.'
     respectively.

`SELECT CASE'
     Not fully implemented.  *Note `SELECT CASE' on `CHARACTER' Type:
     SELECT CASE on CHARACTER Type.

Specification statements
     A limited subset of the Fortran 90 syntax and semantics for
     variable declarations is supported, including `KIND'.  *Note Kind
     Notation::.  (`KIND' is of limited usefulness in the absence of the
     `KIND'-related intrinsics, since these intrinsics permit writing
     more widely portable code.)  An example of supported `KIND' usage
     is:
          INTEGER (KIND=1) :: FOO=1, BAR=2
          CHARACTER (LEN=3) FOO
     `PARAMETER' and `DIMENSION' attributes aren't supported.


File: g77.info,  Node: Other Dialects,  Next: Other Compilers,  Prev: Compiler,  Up: Top

Other Dialects
**************

   GNU Fortran supports a variety of features that are not considered
part of the GNU Fortran language itself, but are representative of
various dialects of Fortran that `g77' supports in whole or in part.

   Any of the features listed below might be disallowed by `g77' unless
some command-line option is specified.  Currently, some of the features
are accepted using the default invocation of `g77', but that might
change in the future.

   _Note: This portion of the documentation definitely needs a lot of
work!_

* Menu:

* Source Form::       Details of fixed-form and free-form source.
* Trailing Comment::  Use of `/*' to start a comment.
* Debug Line::        Use of `D' in column 1.
* Dollar Signs::      Use of `$' in symbolic names.
* Case Sensitivity::  Uppercase and lowercase in source files.
* VXT Fortran::       ...versus the GNU Fortran language.
* Fortran 90::        ...versus the GNU Fortran language.
* Pedantic Compilation::  Enforcing the standard.
* Distensions::       Misfeatures supported by GNU Fortran.


File: g77.info,  Node: Source Form,  Next: Trailing Comment,  Up: Other Dialects

Source Form
===========

   GNU Fortran accepts programs written in either fixed form or free
form.

   Fixed form corresponds to ANSI FORTRAN 77 (plus popular extensions,
such as allowing tabs) and Fortran 90's fixed form.

   Free form corresponds to Fortran 90's free form (though possibly not
entirely up-to-date, and without complaining about some things that for
which Fortran 90 requires diagnostics, such as the spaces in the
constant in `R = 3 . 1').

   The way a Fortran compiler views source files depends entirely on the
implementation choices made for the compiler, since those choices are
explicitly left to the implementation by the published Fortran
standards.  GNU Fortran currently tries to be somewhat like a few
popular compilers (`f2c', Digital ("DEC") Fortran, and so on).

   This section describes how `g77' interprets source lines.

* Menu:

* Carriage Returns::  Carriage returns ignored.
* Tabs::              Tabs converted to spaces.
* Short Lines::       Short lines padded with spaces (fixed-form only).
* Long Lines::        Long lines truncated.
* Ampersands::        Special Continuation Lines.


File: g77.info,  Node: Carriage Returns,  Next: Tabs,  Up: Source Form

Carriage Returns
----------------

   Carriage returns (`\r') in source lines are ignored.  This is
somewhat different from `f2c', which seems to treat them as spaces
outside character/Hollerith constants, and encodes them as `\r' inside
such constants.


File: g77.info,  Node: Tabs,  Next: Short Lines,  Prev: Carriage Returns,  Up: Source Form

Tabs
----

   A source line with a <TAB> character anywhere in it is treated as
entirely significant--however long it is--instead of ending in column
72 (for fixed-form source) or 132 (for free-form source).  This also is
different from `f2c', which encodes tabs as `\t' (the ASCII <TAB>
character) inside character and Hollerith constants, but nevertheless
seems to treat the column position as if it had been affected by the
canonical tab positioning.

   `g77' effectively translates tabs to the appropriate number of
spaces (a la the default for the UNIX `expand' command) before doing
any other processing, other than (currently) noting whether a tab was
found on a line and using this information to decide how to interpret
the length of the line and continued constants.


File: g77.info,  Node: Short Lines,  Next: Long Lines,  Prev: Tabs,  Up: Source Form

Short Lines
-----------

   Source lines shorter than the applicable fixed-form length are
treated as if they were padded with spaces to that length.  (None of
this is relevant to source files written in free form.)

   This affects only continued character and Hollerith constants, and
is a different interpretation than provided by some other popular
compilers (although a bit more consistent with the traditional
punched-card basis of Fortran and the way the Fortran standard
expressed fixed source form).

   `g77' might someday offer an option to warn about cases where
differences might be seen as a result of this treatment, and perhaps an
option to specify the alternate behavior as well.

   Note that this padding cannot apply to lines that are effectively of
infinite length--such lines are specified using command-line options
like `-ffixed-line-length-none', for example.


File: g77.info,  Node: Long Lines,  Next: Ampersands,  Prev: Short Lines,  Up: Source Form

Long Lines
----------

   Source lines longer than the applicable length are truncated to that
length.  Currently, `g77' does not warn if the truncated characters are
not spaces, to accommodate existing code written for systems that
treated truncated text as commentary (especially in columns 73 through
80).

   *Note Options Controlling Fortran Dialect: Fortran Dialect Options,
for information on the `-ffixed-line-length-N' option, which can be
used to set the line length applicable to fixed-form source files.


File: g77.info,  Node: Ampersands,  Prev: Long Lines,  Up: Source Form

Ampersand Continuation Line
---------------------------

   A `&' in column 1 of fixed-form source denotes an arbitrary-length
continuation line, imitating the behavior of `f2c'.


File: g77.info,  Node: Trailing Comment,  Next: Debug Line,  Prev: Source Form,  Up: Other Dialects

Trailing Comment
================

   `g77' supports use of `/*' to start a trailing comment.  In the GNU
Fortran language, `!' is used for this purpose.

   `/*' is not in the GNU Fortran language because the use of `/*' in a
program might suggest to some readers that a block, not trailing,
comment is started (and thus ended by `*/', not end of line), since
that is the meaning of `/*' in C.

   Also, such readers might think they can use `//' to start a trailing
comment as an alternative to `/*', but `//' already denotes
concatenation, and such a "comment" might actually result in a program
that compiles without error (though it would likely behave incorrectly).


File: g77.info,  Node: Debug Line,  Next: Dollar Signs,  Prev: Trailing Comment,  Up: Other Dialects

Debug Line
==========

   Use of `D' or `d' as the first character (column 1) of a source line
denotes a debug line.

   In turn, a debug line is treated as either a comment line or a
normal line, depending on whether debug lines are enabled.

   When treated as a comment line, a line beginning with `D' or `d' is
treated as if it the first character was `C' or `c', respectively.
When treated as a normal line, such a line is treated as if the first
character was <SPC> (space).

   (Currently, `g77' provides no means for treating debug lines as
normal lines.)


File: g77.info,  Node: Dollar Signs,  Next: Case Sensitivity,  Prev: Debug Line,  Up: Other Dialects

Dollar Signs in Symbol Names
============================

   Dollar signs (`$') are allowed in symbol names (after the first
character) when the `-fdollar-ok' option is specified.

