Rules and Restrictions for Fields

Fields that are type declarations use the identical syntax of normal FORTRAN type statements. All f77 types are allowed, subject to the following rules and restrictions:

• Any dimensioning needed must be in the type statement. The DIMENSION statement has no effect on field names.

• You can specify the pseudo-name %FILL for a field name. %FILL is provided for compatibility with other versions of FORTRAN. It is not needed in f77 because the alignment problems are taken care of for you. It may be a useful feature if you want to make one or more fields that you cannot reference in some particular subroutine. The only thing that %FILL does is provide a field of the specified size and type, and preclude referencing it.

• You must explicitly type all field names. The IMPLICIT statement does not apply to statements in a STRUCTURE declaration, nor do the implicit I,J,K,L,M,N rules apply.

• You cannot use arrays with adjustable or assumed size in field declarations, nor can you include passed-length CHARACTER declarations.

In a structure declaration, the offset of field n is the offset of the preceding field, plus the length of the preceding field, possibly corrected for any adjustments made to maintain alignment. See Appendix C, Data Representations for a summary of storage allocation.