Preface - Adobe

CHAPTER 3
3.3 Data Types and Objects
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Language
All data accessible to PostScript programs, including procedures that are part of
the programs themselves, exists in the form of objects. Objects are produced, manipulated,
and consumed by the PostScript operators. They are also created by
the scanner and executed by the interpreter.
Each object has a type, some attributes, and a value. Objects contain their own dynamic
types; that is, an object’s type is a property of the object itself, not of where
it is stored or what it is called. Table 3.2 lists all the object types supported by the
PostScript language. Extensions to the language may introduce additional object
types. The distinction between simple and composite objects is explained below.
TABLE 3.2 Types of objects
SIMPLE OBJECTS COMPOSITE OBJECTS
boolean array
fontID dictionary
integer file
mark gstate (LanguageLevel 2)
name packedarray (LanguageLevel 2)
null save
operator string
real
3.3.1 Simple and Composite Objects
Objects of most types are simple, atomic entities. An atomic object is always constant—a
2 is always a 2. There is no visible substructure in the object; the type, attributes,
and value are irrevocably bound together and cannot be changed.
However, objects of certain types indicated in Table 3.2 are composite. Their
values are separate from the objects themselves; for some types of composite object,
the values have internal substructure that is visible and can sometimes be