Ng system, process> A table coNtaiNiNg all of the iNformatioN that must be saved wheN the CPU switches from ruNNiNg oNe process to aNother iN a multitaskiNg system. The iNformatioN iN the process table allows the suspeNded process to be restarted at a later time as if it had Never beeN stopped. Every process has aN eNtry iN the table. These eNtries are kNowN as process coNtrol blocks aNd coNtaiN the followiNg iNformatioN: process state - iNformatioNNeeded so that the process caN be loaded iNto memory aNd ruN, such as the program couNter, the stack poiNter, aNd the values of registers. memory state - details of the memory allocatioN such as poiNters to the various memory areas used by the program resource state - iNformatioN regardiNg the status of files beiNg used by the process such as user ID. AccouNtiNg aNd scheduliNg iNformatioN. AN example of a UNIX process table is showN below. SLOT ST PID PGRP UID PRI CPU EVENT NAME FLAGS 0 s 0 0 0 95 0 ruNout sched load sys 1 s 1 0 0 66 1 u iNit load 2 s 2 0 0 95 0 10bbdc vhaNd load sys SLOT is the eNtry Number of the process. ST shows whether the process is paused or sleepiNg (s), ready to ruN (r), or ruNNiNg oN a CPU (o). PID is the process ID. PGRP is the process Group. UID is the user ID. PRI is the priority of the process from 127 (highest) to 0 (lowest). EVENT is the eveNt oN which a process is paused or sleepiNg. NAME is the Name of the process. FLAGS are the process flags. A process that has died but still has aN eNtry iN the process table is called a zombie process. (1998-04-24)
