Nucleus

Process Hierarchy

Inherited from THE's hierarchical structure, Nucleus implements process hierarchy.

Parent process can start, stop, remove its own children.

Why?

Support OS development.

Micro kernel.

How?

1. Sequential proccesses
2. Message Passing

Message Passing

Used to transfer information among processes. IPC + Sync.

A common pool of Message buffers + Message queue for each process.

DIS Always go through Nucleus to make the message passing happen.

Dummy answer: sent to the senders when a process with unanswered messages is removed.

Isolation: No process can interfere with a conversation between two other processes. Done by storing the identity of the sender and receiver in each buffer and checking it whenever a process attempts to send or wait for an answer in a given buffer.

Internal Process

Normal process.

External Process

Special process abstraction for device I/O. It is message based.

• Try to use a few uniformed abstractions everywhere in the system.