Explicitly specifies the properties of data objects or functions. Type declarations must precede all executable statements, can be declared only once, and cannot be used to change the type of a symbolic name that has already been implicitly assumed to be another type. Type declaration statements can initialize data in the same way as the DATA statement: by having values, bounded by slashes, listed immediately after the symbolic name of the entity.
1 – Numeric
Statement format:
type[*n] [[,att]...::] v [*n][/clist/][,v [*n][/clist/]]...
type Is any of the following data type specifiers:
BYTE (equivalent to INTEGER*1) DOUBLE PRECISION
LOGICAL COMPLEX
INTEGER DOUBLE COMPLEX
REAL
n Is an integer that specifies (in bytes) the length
of "v". It overrides the length that is implied by
the data type.
The value of n must specify an acceptable length
for the type of "v" (see the HP Fortran for OpenVMS
Language Reference Manual). BYTE, DOUBLE PRECISION,
and DOUBLE COMPLEX data types have one acceptable
length; thus, for these data types, the "n" specifier
is invalid.
If an array declarator is used, the "n" specifier
must be positioned immediately after the array name.
att Is one of the following attribute specifiers:
ALLOCATABLE POINTER
AUTOMATIC PRIVATE
DIMENSION PUBLIC
EXTERNAL SAVE
INTENT STATIC
INTRINSIC TARGET
OPTIONAL VOLATILE
PARAMETER
v Is the name of a data object or function. It can
optionally be followed by:
o An array specification, if the object is an array
o A character length, if the object is of type
character
o An initialization expression or, for pointer
objects, =>NULL()
clist Is a list of constants, as in a DATA statement. If
"v" is the symbolic name of a constant, the "clist"
cannot be present.
A numeric data type declaration statement can define arrays by
including array specifications in the list.
A numeric type declaration statement can assign initial values to
variables or arrays if it specifies a list of constants (the
"clist"). The specified constants initialize only the variable or
array that immediately precedes them. The "clist" cannot have more
than one item unless it initializes an array. When the "clist"
initializes an array, it must contain a value for every element in
the array.
If =>NULL() appears for a pointer, the pointer's initial
association status is disassociated.
In a function declaration, an array must be a deferred-shape array
if it has the POINTER attribute; otherwise, it must be an
explicit-shape array.
The double colon separator (::) is required only if the declaration
contains an attribute specifier or an initialization expression;
otherwise it is optional.
The same attribute must not appear more than once in a given type
declaration statement, and an entity cannot be given the same
attribute more than once in a scoping unit.
If the PARAMETER attribute is specified, the declaration must
contain an initialization expression.
The following objects cannot be initialized in a type declaration
statement:
o A dummy argument
o A function result
o An object in a named common block (unless the type declaration
is in a block data program unit)
o An object in blank common
o An allocatable array
o A pointer
o An external name
o An intrinsic name
o An automatic object
o An object that has the AUTOMATIC attribute
2 – Character
Format:
CHARACTER[*len[,] [[,att]...::] v[*len] [/clist/]
[,v[*len] [/clist/]]...
len Is an unsigned integer constant, an integer constant
expression enclosed in parentheses, or an asterisk (*)
enclosed in parentheses. The value of "len" specifies
the length of the character data elements.
att Is one of the following attribute specifiers:
ALLOCATABLE POINTER
AUTOMATIC PRIVATE
DIMENSION PUBLIC
EXTERNAL SAVE
INTENT STATIC
INTRINSIC TARGET
OPTIONAL VOLATILE
PARAMETER
v Is the symbolic name of a constant, variable, array,
statement function or function subprogram, or array
specification. The name can optionally be followed by
a data type length specifier (*len or *(*)).
clist Is a list of constants, as in a DATA statement. If
"v" is the symbolic name of a constant, "clist" must
not be present.
If you use CHARACTER*len, "len" is the default length specification
for that list. If an item in that list does not have a length
specification, the item's length is "len". However, if an item
does have a length specification, it overrides the default length
specified in CHARACTER*len.
When an asterisk length specification *(*) is used for a function
name or dummy argument, it assumes the length of the corresponding
function reference or actual argument. Similarly, when an asterisk
length specification is used for the symbolic name of a constant,
the name assumes the length of the actual constant it represents.
For example, STRING assumes a 9-byte length in the following
statements:
CHARACTER*(*) STRING
PARAMETER (STRING = 'VALUE IS:')
The length specification must range from 1 to 65535. If no length
is specified, a length of 1 is assumed.
Character type declaration statements can define arrays if they
include array specifications in their list. The array
specification goes first if both an array specification and a
length are specified.
A character type declaration statement can assign initial values to
variables or arrays if it specifies a list of constants (the
clist). The specified constants initialize only the variable or
array that immediately precedes them. The "clist" cannot have more
than one element unless it initializes an array. When the "clist"
initializes an array, it must contain a value for every element in
the array.
In a function declaration, an array must be a deferred-shape array
if it has the POINTER attribute; otherwise, it must be an
explicit-shape array.
The double colon separator (::) is required only if the declaration
contains an attribute specifier or an initialization expression;
otherwise it is optional.
The same attribute must not appear more than once in a given type
declaration statement, and an entity cannot be given the same
attribute more than once in a scoping unit.
If the PARAMETER attribute is specified, the declaration must
contain an initialization expression.
The following objects cannot be initialized in a type declaration
statement:
o A dummy argument
o A function result
o An object in a named common block (unless the type declaration
is in a block data program unit)
o An object in blank common
o An allocatable array
o A pointer
o An external name
o An intrinsic name
o An automatic object
o An object that has the AUTOMATIC attribute
NOTE
The CHARACTER*len form for a CHARACTER declaration
is obsolescent in Fortran 95. VSI Fortran flags
obsolescent features, but fully supports them.