CBJECl'S AND OPERATORS
2-2. CBJECl'ADDRESSING AND GLCBAL SIDRAGE MANAGEMENT
Object addressing on the IP follows the same three level sequence as on a GOP. The steps taken to address an object are:
1.Given an access descriptor, a processor uses the directory
index field to index the object table directory and gain a storage descr iptor for the o~ect table which contains an object reference for the desir #object.
2.With the storage descriptor for the object table and the segment index field of the access descriptor, the processor locates a storage descriptor for the requested object.
3.The storage descriptor for the object contains the base and length information required to locate the object in 432 :mennry.
An IP can he directed to manipulate objects in 432 memory, just as other 432 processors, hut lacks any facility to create objects. All original objects used by an IP rust be predefined and loaded into 432 memory at system initialization time. Additional objects, which may be required, must be created by a GOP process (e.g. the storage manager) •
A 432 operating system type manager might maintain a template for a prototype IP process. When i t received a request for a new IP process from the I/O oontroller the GOP would build one using the prototype and then return it via the standard communication port mechanism.
The IP suW'rts the same program environment hierarchy (process, context, domain) as a GOP but implements each level differently.
The IP does not require that a domain object be implemented but the oontext object contains a slot for an access descriptor for a domain object should one be required. When implemented, IP domains do not contain instruction segments (since the IP does not fetch instructions) or operand stack segments. The danain may be used to store same static information which may be required by a process.
An IP context is a refinement of an IP process object. Each IP process is bound to a single context for the lifet~ of the process. An environment is changed by invoking the ENTER ACCE'SS SEG1ENT or ENTER GLCBAL AOCESS SEGfENr functions.
