Operating Systems Structure1- Explain briefly why the objectives o.pdf

Operating Systems Structure 1- Explain briefly why the objectives of a purely batch multiprogramming operating system conflict with those of an interactive system. 2- What features from the Mainframe operating system Multics do we see in modern operating systems? Solution Answer 2.. The various features of Multics are : -Segmented memory -Virtual memory -High-level language implementation -Shared memory multiprocessor -Multi-language support -Relational database -Security -On-line reconfiguration -Software engineering Out of the above features, the feature that are present in modern operating system are: 1) security Each user has to be authenticated with an username and password (network and multi-user operating system). Their data and files will be kept private from other users, unless they choose to make some shareable with others. The operating system will only allow administrators (\'super users\') to change parts of the operating system and install applications. 2)Segmented memory To use shared memory, we have to perform 2 basic steps: Request to the operating system a memory segment that can be shared between processes. The user can create/destroy/open this memory using a shared memory object: An object that represents memory that can be mapped concurrently into the address space of more than one process.. Associate a part of that memory or the whole memory with the address space of the calling process. The operating system looks for a big enough memory address range in the calling process\' address space and marks that address range as an special range. Changes in that address range are automatically seen by other process that also have mapped the same shared memory object. 3)Virtual memory Virtual memory is a memory management capability of an OS that uses hardware and software to allow a computer to compensate for physical memory shortages by temporarily transferring data from random access memory (RAM) to disk storage. Virtual address space is increased using active memory in RAM and inactive memory in hard disk drives (HDDs) to form contiguous addresses that hold both the application and its data. 4)Shared memory multiprocessor Shared memory is the fastest interprocess communication mechanism. The operating system maps a memory segment in the address space of several processes, so that several processes can read and write in that memory segment without calling operating system functions. However, we need some kind of synchronization between processes that read and write shared memory. Consider what happens when a server process wants to send an HTML file to a client process that resides in the same machine using network mechanisms: The server must read the file to memory and pass it to the network functions, that copy that memory to the OS\'s internal memory. The client uses the network functions to copy the data from the OS\'s internal memory to its own memory. As we can see, there are two copies, one from memory to the network an.