BLOCK_DATA

 Begins a block data program unit.  Statement format:

    BLOCK DATA [nam]
      [stmts]
    END [BLOCK DATA [nam]]

    nam   Is the symbolic name used to identify the block.  
    
    stmts Is one or more of the following statements:

           COMMON        PARAMETER  Type declaration
           DATA          POINTER    Derived-type definition  
           DIMENSION     RECORD     Record structure declaration
           EQUIVALENCE   SAVE
           IMPLICIT      TARGET
           INTRINSIC     USE

    Note: A type declaration cannot contain the ALLOCATABLE,
          EXTERNAL, INTENT, OPTIONAL, PRIVATE, or PUBLIC
          attributes.

 A BLOCK DATA statement and its associated specification statements
 are a special kind of program unit, called a block data subprogram.

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

 A block data subprogram must not contain any executable statements.

 As with other types of program units, the last statement in a block
 data subprogram must be an END statement.  If a name follows the
 END statement, it must be the same as the name specified in the
 BLOCK DATA statement.

 Within a block data subprogram, if a DATA statement initializes any
 entity in a named common block, the subprogram must have a complete
 set of specification statements that establishes the common block.
 However, all of the entities in the block do not have to be
 assigned initial values in a DATA statement.

 One block data subprogram can establish and define initial values
 for more than one common block.

 The name of a block data subprogram 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.