Consider a program that creates a child process, and then in the child closes standard output (STDOUT FILENO). What happens if the child calls printfO to print something after closing the descriptor? Can the parent print something using printf after the child process closes STDOUT_FILENO? Describe how arguments of functions are passed between the user-level implementation of a system call and its kernel-level implementation. Illustrate your answer with code extract from OS/161 What are the main states of a thread/process in OS/161? In OS/161, what happens when a thread terminates? Explain what the functions thread_ exit0, exorcise0, and thread_ destroy0 do when threads terminate