gtpd1m2eDatabase Reference

OBJECT Class

As previously mentioned, every class in TPFCS has the OBJECT class as its base class; that is, all classes inherit from the OBJECT class. For this reason, all objects are said to have an object header, which consists of the attributes of OBJECT.

Object Header

The object header contains the following data in the order presented:

Object ID (class ID)
A 4-byte field containing a hexadecimal value known as the class ID of the object. The class ID stored in this field for a given object represents its most detailed classification. This field is the same attribute discussed in our previous abstract examples and identified an object as being either a Limousine or a ClassC object, and so on. The class IDs of all of the objects used by TPFCS are defined by CLASSID macro statements in the ITO2 DSECT.

Update sequence counter
A 4-byte sequence counter field used by some application programming interfaces (APIs).

Object length
A 4-byte field containing the length of the object when it is brought into memory.

The value stored in this field will include the lengths of all attributes inherited from higher classes, including the length of the object header itself.

spare
An additional 4 bytes is reserved for future use by IBM.