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(g77-300.info)Run-time Environment Limits


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Run-time Environment Limits
===========================

   As a portable Fortran implementation, `g77' offers its users direct
access to, and otherwise depends upon, the underlying facilities of the
system used to build `g77', the system on which `g77' itself is used to
compile programs, and the system on which the `g77'-compiled program is
actually run.  (For most users, the three systems are of the same
type--combination of operating environment and hardware--often the same
physical system.)

   The run-time environment for a particular system inevitably imposes
some limits on a program's use of various system facilities.  These
limits vary from system to system.

   Even when such limits might be well beyond the possibility of being
encountered on a particular system, the `g77' run-time environment has
certain built-in limits, usually, but not always, stemming from
intrinsics with inherently limited interfaces.

   Currently, the `g77' run-time environment does not generally offer a
less-limiting environment by augmenting the underlying system's own
environment.

   Therefore, code written in the GNU Fortran language, while
syntactically and semantically portable, might nevertheless make
non-portable assumptions about the run-time environment--assumptions
that prove to be false for some particular environments.

   The GNU Fortran language, the `g77' compiler and run-time
environment, and the `g77' documentation do not yet offer comprehensive
portable work-arounds for such limits, though programmers should be
able to find their own in specific instances.

   Not all of the limitations are described in this document.  Some of
the known limitations include:

Timer Wraparounds
Year 2000 (Y2K) Problems
Array Size
Character-variable Length
Year 10000 (Y10K) Problems

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