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| (operating system, process) | process table - 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 - information needed 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. | |
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