3. Context of a process in a unix .pptx
- 1. Context of a process
- 2. • The context of a process is its state or mode in which a process runs. The PROCESS can Run in Two modes: Kernel mode User mode
- 3. Kernel mode • Is commonly referred to as the supervisor mode . • System processes such as swapping, memory allocation , house keeping and administrative functions, run in kernel mode.
- 4. User mode • Is the mode in which user processes run. • User process such as application programs, utility programs run in user mode, but switch to kernel mode when there is an exception or system call.
- 5. Differences between kernel mode and user mode Kernel mode User mode 1. Executing code has complete and unrestricted access to the underlying hardware. 1. Executing code has no ability to directly access hardware or reference memory. 2. It can execute any CPU instruction and reference any memory address. 2. It can not execute. 3. Crashes in kernel mode are catastrophic; they will halt the entire PC. 3. Crashes in user mode are always recoverable. 4. It cannot be arbitrarily suspended and replaced by another process. 4. It can be interrupted by an interrupt or an exception. 5. A process running in kernel mode can read or write directly to OS memory. 5. A process running in user mode can't read or write directly to OS memory. 6. Programs run in system level. 6. Programs run in a application level. 7. Kernel mode has higher priority. 7. User mode has lower priority.