GNU Info

(g77-295.info)Star Notation

---

Next: Kind Notation Prev: Double Notation Up: Types

---

Enter node , (file) or (file)node

Star Notation
.............

   The following notation specifies the storage size for a type:

     GENERIC-TYPE*N

GENERIC-TYPE must be a generic type--one of `INTEGER', `REAL',
`COMPLEX', `LOGICAL', or `CHARACTER'.  N must be one or more digits
comprising a decimal integer number greater than zero.

   Use the above form where a type name is valid.

   The `*N' notation specifies that the amount of storage occupied by
variables and array elements of that type is N times the storage
occupied by a `CHARACTER*1' variable.

   This notation might indicate a different degree of precision and/or
range for such variables and array elements, and the functions that
return values of types using this notation.  It does not limit the
precision or range of values of that type in any particular way--use
explicit code to do that.

   Further, the GNU Fortran language requires no particular values for
N to be supported by an implementation via the `*N' notation.  `g77'
supports `INTEGER*1' (as `INTEGER(KIND=3)') on all systems, for example,
but not all implementations are required to do so, and `g77' is known
to not support `REAL*1' on most (or all) systems.

   As a result, except for GENERIC-TYPE of `CHARACTER', uses of this
notation should be limited to isolated portions of a program that are
intended to handle system-specific tasks and are expected to be
non-portable.

   (Standard FORTRAN 77 supports the `*N' notation for only
`CHARACTER', where it signifies not only the amount of storage
occupied, but the number of characters in entities of that type.
However, almost all Fortran compilers have supported this notation for
generic types, though with a variety of meanings for N.)

   Specifications of types using the `*N' notation always are
interpreted as specifications of the appropriate types described in
this document using the `KIND=N' notation, described below.

   While use of this notation is popular, it doesn't serve well in the
context of a widely portable dialect of Fortran, such as the GNU
Fortran language.

   For example, even on one particular machine, two or more popular
Fortran compilers might well disagree on the size of a type declared
`INTEGER*2' or `REAL*16'.  Certainly there is known to be disagreement
over such things among Fortran compilers on *different* systems.

   Further, this notation offers no elegant way to specify sizes that
are not even multiples of the "byte size" typically designated by
`INTEGER*1'.  Use of "absurd" values (such as `INTEGER*1000') would
certainly be possible, but would perhaps be stretching the original
intent of this notation beyond the breaking point in terms of
widespread readability of documentation and code making use of it.

   Therefore, this document uses "star notation" only on occasion for
the benefit of those readers who are accustomed to it.