After the marketing hype cooled, object libraries continued to be used in both object-oriented programming and distributed information systems. Class libraries are the rough OOP equivalent of older types of code libraries. They contain classes, which describe characteristics and define actions (methods) that involve objects. Class libraries are used to create instances, or objects with their characteristics set to specific values. In some OOP languages, like Java, the distinction is clear, with the classes often contained in library files (like Java's JAR file format) and the instantiated objects residing only in memory (although potentially able to be made persistent in separate files). In others, like Smalltalk, the class libraries are merely the starting point for a system image that includes the entire state of the environment, classes and all instantiated objects.