# BLOCK DATA

Statement: Identifies a block-data program unit, which provides initial values for variables in named common blocks. BLOCK DATA is an obsolescent language feature in Standard Fortran.

BLOCK DATA [name]

[specification-part]

END [BLOCK DATA [name]]

name | Is the name of the block data program unit.
specification-part | Is one or more of the following statements:
COMMON | INTRINSIC | STATIC
DATA | PARAMETER | TARGET
Derived-type definition | POINTER | Type declaration 2
DIMENSION | RECORD1 | USE 3
EQUIVALENCE | Record structure declaration1 |
IMPLICIT | SAVE |
1 For more information, see RECORD statement and record structure declarations. 2 Can only contain attributes: DIMENSION, INTRINSIC, PARAMETER, POINTER, SAVE, STATIC, or TARGET. 3 Allows access to only named constants.

## Description

A block data program unit need not be named, but there can only be one unnamed block data program unit in an executable program.

If a name follows the END statement, it must be the same as the name specified in the BLOCK DATA statement.

An interface block must not appear in a block data program unit and a block data program unit must not contain any executable statements.

If a DATA statement initializes any variable in a named common block, the block data program unit must have a complete set of specification statements establishing the common block. However, all of the variables in the block do not have to be initialized.

A block data program unit can establish and define initial values for more than one common block, but a given common block can appear in only one block data program unit in an executable program.

The name of a block data program unit can appear in the EXTERNAL statement of a different program unit to force a search of object libraries for the block data program unit at link time.

## Example

The following shows a block data program unit:

    BLOCK DATA BLKDAT
      INTEGER S,X
      LOGICAL T,W
      DOUBLE PRECISION U
      DIMENSION R(3)
      COMMON /AREA1/R,S,U,T /AREA2/W,X,Y
      DATA R/1.0,2*2.0/, T/.FALSE./, U/0.214537D-7/, W/.TRUE./, Y/3.5/
    END

The following shows another example:

    C      Main Program
           CHARACTER(LEN=10) family
           INTEGER a, b, c, d, e
           REAL X(10), Y(4)
           COMMON/Lakes/a,b,c,d,e,family/Blk2/x,y
           ...
    C      The following block-data subprogram initializes
    C      the named common block /Lakes/:
    C
           BLOCK DATA InitLakes
           COMMON /Lakes/ erie, huron, michigan, ontario,
          +        superior, fname
           DATA erie, huron, michigan, ontario, superior /1, 2, 3, 4, 5/
           CHARACTER(LEN=10) fname/'GreatLakes'/
           INTEGER erie, huron, michigan, ontario, superior
           END

Parent topic: A to B

## See Also

COMMON
DATA
EXTERNAL
Program Units and Procedures
Obsolescent Language Features in the Fortran Standard