<P> In a switch, the state of process currently executing must be saved somehow, so that when it is rescheduled, this state can be restored . </P> <P> The process state includes all the registers that the process may be using, especially the program counter, plus any other operating system specific data that may be necessary . This is usually stored in a data structure called a process control block (PCB) or switchframe . </P> <P> The PCB might be stored on a per - process stack in kernel memory (as opposed to the user - mode call stack), or there may be some specific operating system defined data structure for this information . A handle to the PCB is added to a queue of processes that are ready to run, often called the ready queue . </P> <P> Since the operating system has effectively suspended the execution of one process, it can then switch context by choosing a process from the ready queue and restoring its PCB . In doing so, the program counter from the PCB is loaded, and thus execution can continue in the chosen process . Process and thread priority can influence which process is chosen from the ready queue (i.e., it may be a priority queue). </P>

Which one of the following when added can reduce the processing time of a computer