Initializes program variables.
Syntax
DATA var-list1 / val-list1 / [[,]var-list2 / val-list2 /]... |
 |
- var-list
is a comma-separated list of entities, including
the following:
An array triplet section; for example:
An array element reference; for example:
A substring name; for example:
An implied-DO
loop; for example:
((matrix(i,j),i=0,5),j=5,10) |
An object of a derived type
A component of a derived-type object
The following cannot appear in var-list:
Records and record field references. However, you
can initialize a record's fields in the record's
structure definition. See “RECORD (extension)”.
Automatic objects, including automatic character
strings
Allocatable arrays: that is, arrays declared with
a specified rank, but no specified bounds within each dimension
The result variable of a function
Objects made available by use or host association
- val-list
is a list of constant values, separated by commas.
Each constant in the list represents a value to be assigned to the
corresponding variable in var-list. A
constant value can be optionally repeated by preceding the constant
with a repetition factor. The syntax of a repeated constant is:
r*val
where r is a positive integer specifying
the number of times that val, the constant
value, is to be specified.
Description
The DATA statement initializes
variables local to a program unit before the program unit begins
execution. Initialization occurs as follows:
The var-list is expanded to form a sequence of scalar variables,
and the val-list is expanded to form a sequence of scalar constants.
The number of items in each expanded sequence must be the same,
and there must be a one-to-one correspondence between the items
in the two expanded lists. The variables in the expanded sequence
of var-list are initialized on the basis of the correspondence.
If var-list contains an array name,
the expanded sequence of constants must contain a constant for every
element in the array.
A zero-sized array or an implied-DO
list with an iteration count of zero in var-list
contributes no variables to the expanded sequence of variables.
However, a zero-length character variable does contribute a variable
to the list.
If a constant is of any numeric or logical type, the corresponding
variable can be of any numeric type. If an object is of derived
type, the corresponding constant must be of the same type. If the
type of the constant does not agree with the type of the variable,
type conversion is performed, as described in Table 5-5 “Conversion of variable=expression”.
Variables can be initialized with binary, octal, or hexadecimal
constants.
A variable or array element must not appear in a DATA
statement more than once. If two variables share the same storage
space through an EQUIVALENCE
statement, only one can appear in a DATA
statement. If a substring of a character variable or other array
element appears in a DATA
statement, no overlapping substring (including the entire variable
or array element) can appear in any DATA
statement.
The length of a character constant and the declared length
of its corresponding character variable need not be the same. If
the constant is shorter than the variable, blank characters are
placed in the remaining positions. If the constant is longer than
the variable, the constant is truncated from the right until it
is the same length as the variable
If a subscripted array element appears in var-list,
then the subscript must be a specification expression.
DATA statements
can be interspersed among executable statements. However, they initialize
prior to runtime and, therefore, cannot be used as executable assignment
statements.
Fortran 90 extensions
A variable of type other than integer may be initialized with
a binary, octal, or hexadecimal constant. The data type for a constant
is determined from the type of the corresponding variable. The size
(in bytes) of the variable determines how many digits of the octal
or hexadecimal constant are used. If the constant lacks enough digits,
the value is padded on the left with zeros. If the constant has
too many digits, it is truncated on the left.
An integer, binary, octal, or hexadecimal constant can initialize
a character variable of length one, as long as the value of the
constant is in the range 0 to 255.
Examples
The following DATA
statement initializes integer, logical, and character variables:
INTEGER i
LOGICAL done
CHARACTER(LEN=5) prompt
DATA i, done, prompt/10, .FALSE., "Next?"/ |
The next DATA
statement specifies a repetition factor of 3 to assign the value
of 2 to all three elements of array i:
INTEGER, DIMENSION(3) :: i
DATA i/3*2/ |
The next DATA
statement uses two nested implied-DO
loops to assign the literal value X
to each element of an array of 50 elements, k(10,5):
CHARACTER, DIMENSION(10,5) :: k
DATA ((k(i,j),i=1,10),j=1,5)/50*"X"/ |
Related statements
BYTE, CHARACTER,
COMPLEX, DOUBLE COMPLEX,
DOUBLE PRECISION,
INTEGER, LOGICAL,
and REAL
Related concepts
For related information, see the following:
Printable version
