Language Reference

Block Data Program Unit

A block data program unit provides initial values for objects in named common blocks.

>>-BLOCK_DATA_statement----------------------------------------><
 
 

>>-+--------------------+--------------------------------------><
   '-specification_part-'
 
 

>>-END_BLOCK_DATA_statement------------------------------------><
 
 

BLOCK_DATA_statement

See BLOCK DATA for syntax details

specification_part

is a sequence of statements from the statement groups numbered (2), (3), and (4) in Order of Statements and Execution Sequence

END_BLOCK_DATA_statement

See END for syntax details

In specification_part, you can specify type declaration, USE, IMPLICIT, COMMON, DATA, EQUIVALENCE, and integer POINTER statements, derived-type definitions, and the allowable attribute specification statements. The only attributes that can be specified include PARAMETER, DIMENSION, INTRINSIC, POINTER, SAVE, and TARGET.

A type declaration statement in a block data specification-part shall not contain ALLOCATABLE or EXTERNAL attribute specifiers.

You can have more than one block data program unit in an executable program, but only one can be unnamed. You can also initialize multiple named common blocks in a block data program unit.

Restrictions on common blocks in block data program units are:

• All items in a named common block must appear in the COMMON statement, even if they are not all initialized.
• The same named common block must not be referenced in two different block data program units.
• Only nonpointer objects in named common blocks can be initialized in block data program units.
• Objects in blank common blocks cannot be initialized.

Example of a Block Data Program Unit

PROGRAM MAIN
  COMMON /L3/ C, X(10)
  COMMON /L4/ Y(5)
END PROGRAM
BLOCK DATA BDATA
  COMMON /L3/ C, X(10)
  DATA C, X /1.0, 10*2.0/   ! Initializing common block L3
END BLOCK DATA
 
BLOCK DATA                  ! An unnamed block data program unit
  PARAMETER (Z=10)
  DIMENSION Y(5)
  COMMON /L4/ Y
  DATA Y /5*Z/
END BLOCK DATA