1) 1. Kernel-space 2.Kernel-space 3.Users-space 4.Kernel-space 5.User-space 6.User-space2) It takes up much less memory upon boot and their structure is more dynamic. Servers can be started as needed, not all servers are required at boot time. Microkernel usually implement a [pluggable architecture with support for system modules that can be loaded needed and plugged into the kernel. It is more modular and thus more flexible and extensible.

3) Where a single system call is sufficient for conventional operating system, a microkernel uses message passing. Performance can suffer because of the added overhead of communication between objects. The efficiency of functions that stay in Kernel space in conventional operating system is diminished when those functions are moved to user space. Since messages pass between user space and kernel space objects, switches in privilege levels is likely to occur, further complicating performance. Where systems calls work in a single address space for conventional designs, this message passing and privilege switching implies that two or more address spaces must be used to implement a microkernel service request.4) Concept such as virtual memoty pages built from physical memoty frames, demand-paged virtual memoty, and dynamic page replacement combine to give the illusion of ner limitless memory resources, where physical memoty is supported and extended by storage such as hard disk spave.Regarding to issues, Several issues complicate the implementation, such as external fragmentation, which arises when there are many small gaps between allocated memory blocks, which invalidates their use for an allocation request. The allocator's metadata can also inflate the size of (individually) small allocations. This is often managed by chunking. The memory management system must track outstanding allocations to ensure that they do not overlap and that no memory is ever "lost" as a memory leak.The reason why DNN might not work in nanokernel is that it is too complicated. Most of the functions implemented are pre-emptible and primitive. So, they van be fast.5) 1. Process2. Process3. Thread 4. Threads Threads are used for small tasks. Another difference between a thread and a process is that threads within the same process share the same address space, whereas different processes do not . Also, A process can consist of multiple threads.6)Application could use a multiple active objects at the same time, because they run in user space and active have the properties of Symbian threads.Active objects allow blocking I/O calls to be handled by the operating system rather than the process itself. Active objects are coordinated by a single scheduler and implemented in a single thread. It can not call a function and expect a return value. It must call a special function and let that set up the blocking I/O, but return immediately.7)Type of security: the system asked the user for permission to install every installed application. Each software developer is now responsible for verifying her own software through a process called signing.Smartphones provide a difficult environment to make secure. They are single-users devices and require no user authentication to use basic functions. Safequarding this environment is complicated.There are some other forms of file security on Symbian OS.There are areas of the Symbian OS storage medium that applications cannot access without special capability.8)They are single-users devices and require no user identification to use. A phone users can execute applications, dial the phone, and access networks-all without identification. In this environment, using permission-based security is challenging, because the lack of identification means only set of permissions is possible-the same set for everyone.The effect of this is that installed applications after being installed are protected from nonsystem access. In addition, there are areas of the file system reserved specifically for certain types of data manipulation by application.