1. Which situation is suitable to use message passing instead of shared-memory model for communication between processes? What are the pros and cons of using these two models?
When packets of information in predefined formats are moved between processes by the operating system,you can use message passing.
Pros of the Message Passing Model: One of the biggest semantic advantages of the message-passing communication model is the fact that it is, by nature, interrupt driven. Messages combine both data and synchronization in a single unit.
Cons of Message Passing: In addition to requiring the explicit management of data and communication, the message passing paradigm has one intrinsic disadvantage that can be mitigated but not eliminated by good interface design: the presence of higher endpoint costs in message passing models as compared to shared memory.
Pros of the Shared Memory Model:. One of the primary reasons for this is that shared memory shelters programmers from the details of interprocessor communication: the location-independent semantics of shared memory allow programmers to focus on issues of parallelism and correctness while completely ignoring issues of where data is and how to access it. This can allow the “quick construction” of algorithms that communicate implicitly through data structures. In some sense, the shared-memory communication model offers one of the simplest extensions of the uni-processor programming paradigm to multiprocessors
Cons of Shared Memory: One of the deficiencies of the shared-memory communication model is the fact that it is, by nature, a polling interface. While this can make for extremely efficient communication under some circumstances, it can have a negative impact on synchronization operations.
2.functions:
System calls are made from an application program to request the OS to perform certain services that use the resources controlled by the OS.
purposes:
process control，file manipulation，device manipulation，information maintenance，communication，protection
3. Please specify different ways for using the hardware configuration during the system generation (SYSGEN). What are the major differences between these different ways?
modify a copy of the source code of the operation system
creation of tables and the selection of modules from a precompiled library .
construct a system that is completely table driven .