Message passing is useful when smaller numbers of data need to be exchanged, because no conflicts need to be avoided. Shared memory processes use map memory
system calls to gain access to regions of memory owned by other processes.
Message passing advantages are OS will offer the extra support like Link Management, and the programmer burden not too heavy and OS burden heavy.The share memory advantage is programmer burden heavy and OS burden not too heavy and disadvantage is OS can only offer Share Memory space, and not offer any extra support.
2.
It is the communication interface when user program execute with operating system, when user program need operating system to provide service, with calling system call communicate operating system, operating system can check the table according to the system call ID, start executing service routing, and return to user program to finish request.
3.
Used to modify a copy of the source code of the OS and have it re-compiled.
Used to create tables and modules from a precompiled library. The needed modules are linked together to form the generated OS. Construct a system is completely table driven. All the code is always part of the system, and selection occurs at execution time. The size and generality of the generated system and the ease of modification as the hardware configuration changes.