1.-Message passing model is more suitable to use when you are doing something more simple , and protect data from being edited by other who shouldn’t access the file.
-Shared-memory model can simulate the message passing model , but vice versa, it does not work, Shared-memory model has a disadvantage that the data or value might be changed by other process due to the sharing concept, they may be using the same source , but when we run a process to change value, the program which uses that value will all receive the changed value when they execute the program , which may end up messing up the whole system.
-Message passing model has the concept of sending message to others , so other will receive maybe value or data by coping it instead of sharing it , so that things won’t be messed up .
2.
(1)
System calls provide the interface between a running program and the operating system.Typically written in high-level language(C or C++).May need to be written in low-level assembly language.
(2)
The functions thatmake up API typically invoke the actual system calls on behalf of the application programmer.
3.Used to modify a copy of the source code of the OS and have it re-compiled. Data declarations, initializations, and constants, along with conditional compilation, produce an output-object version of the operating system that is tailored to the system decribed.
Used to create tables and the selection modules from a precompiled library. The needed modules are linked together to form the generated OS. The selection allows the library to contain the device drivers for all supported I/O devices, but only those needed are linked into the operating system.