HP DDL D40 Reference Manual page 150

Definition Attributes
Level 88 clauses following a bit map item are rejected by DDL, because level
88 clauses are meaningful only in COBOL, which does not support bit maps.
DDL does not generate language output for an ENUM clause specified with
type BIT, because DDL emits the output for the enumeration when the clause
is defined as type ENUM.
An OCCURS clause cannot apply to a bit map, because no compatible
structure is available in the languages supported by DDL that have bit fields. C
does not support arrays of bit fields. Pascal allocates one word for each signed
bit field in an array and packs unsigned bit fields in an array. TAL supports only
arrays of bit fields that are 1, 2, 4, or 8 bits long, packed inside an array.
A REDEFINES clause cannot apply directly to a bit map, because you cannot
have an equivalent bit map item in TAL or a union of bit map items in C. A
substructure containing bit maps can redefine another data item as long as
such a REDEFINES clause follows DDL rules.
Bit fields in a record cannot be used as keys.
For C, DDL generates bit maps as follows:
If bit-length is greater than 1, the output for field definition is SHORT or
UNSIGNED SHORT. Group definition output is short fieldname:bit-
length or unsigned fieldname:bit-length.
If bit-length is 1, the output for a bit map is unsigned short.
DDL does not generate C output for implicit bit fillers and therefore does
not generate any C code for an implicit byte filler at the end of the
substructure.
The output for an explicit byte filler is a bit field whose name is of the form
filler_n; that is, the output is the same as for other FILLER items. If any
item at the same level as the bit filler has the same generated filler name,
then the filler name ends with the next integer that does not cause the
conflict. You should not try to access bit filler data items or reference the
name of a bit filler.
For COBOL, DDL generates bit maps as follows:
The output for a bit map declared as a field definition is NATIVE-2. DDL
ignores bit-length.
The output for a bit map declared in a group structure is FILLER. Both
named bit fields and filler bit fields have the same number of words as the
bit map.
For FORTRAN, DDL generates bit maps as follows:
The output for a bit map declared as a field definition is INTEGER*2. DDL
ignores bit-length.
Data Definition Language (DDL) Reference Manual—426798-002
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TYPE Clause