Data Definition Language (DDL) Reference Manual (G06.24+)

Definition Attributes
Data Definition Language (DDL) Reference Manual—426798-002
6-55
TYPE Clause
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TAL and Pascal support bit maps outside group structures; however, these bit
maps are packed in pTAL or TAL and unpacked in Pascal. To ensure that bit
maps outside group structures are compatible between languages, DDL
generates 16-bit integer items for bit fields declared as field definitions, with
warning messages in all language outputs except Pascal.
In languages that do not support bit maps, including COBOL, FORTRAN, and
TACL, DDL generates a FILLER item for a bit map outside a group structure.
The FILLER item has a number of words equivalent to the number of words
required for such a bit field specified inside a group structure.
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You can specify a bit map as a filler explicitly, the same way you specify a byte
filler. Unlike a byte filler, however, a bit filler always starts at a new word if the
bit filler follows a nonbit item.
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When the definition of a group structure implies bit fillers, DDL generates the
bit fillers implicitly, in the same way that DDL generates implicit byte fillers.
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The SPI-NULL value for a bit field is 255 by default. Because all bit fields and
bit fillers have the same SPI-NULL value, all bits are turned on in a byte
containing bit items.
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Bit fields that share the same byte must have the same version number in a
token map. The version number applies to the entire byte. If a bit field extends
across 2 bytes within a word, the version number of that field applies to the
entire word.
You specify version numbers in the TOKEN-MAP statement, as shown in the
following example:
DEF bit-ddl-ex-a.
02 bits-8 Type BIT 8.
02 bits-3 Type BIT 3.
02 bits-2 Type BIT 2.
02 bits-10 Type BIT 10.
02 bits-1 Type BIT 1.
END.
TOKEN-MAP bit-map-ex-a VALUE 1 DEF bit-ddl-ex-a.
VERSION "D20" FOR bits-8.
VERSION "D30" FOR bits-3 THRU bits-2.
VERSION "D40" FOR bits-10 THRU bits-1.
END.
For information about version numbers for bit fillers and more examples of
specifying versions, see the TOKEN-MAP Statement on page 7-13.
Note. A variable declared as a simple bit field can be a different size than an
elementary item that is a bit field inside a structure (bit fields are packed within
structures, but might or might not be in a simple bit field). Avoid variables of simple bit
fields in COBOL, FORTRAN, or TACL (which do not support bit maps), or be certain
you know what you are doing in handling such variables.