Operating system states
The operating system can be in one of four states:
The combination of time spent waiting for I/O
and time spent idle
makes up the total time that the operating system spends idle.
executing in user mode
The CPU is
(machine code) of a
that accesses its own data space in memory.
executing in system mode
If a process makes a system call in order to perform
a privileged task requiring the services of the
(such as accessing a disk), then the operating system places
the CPU in
(also known as
idle waiting for I/O
Processes are sleeping while waiting for the completion
of I/O to disk or other block devices.
No processes are
on the CPU or are sleeping
waiting for block I/O.
Processes waiting for keyboard input or network
I/O are counted as idle.
Viewing CPU activity
Tuning CPU resources
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003