System Performance and System Resources
The performance of a computer system depends upon how the system uses and
allocates its resources. Monitor your system's performance regularly so that you know how
it behaves under normal conditions. You should have a good idea of what
to expect, and be able to recognize a problem when it occurs. 
System resources that affect performance are described in the following table.
| System Resource | Description | 
|---|
| Central processing
unit (CPU) | The CPU processes instructions by fetching instructions from memory and executing them.
 | 
| Input/output (I/O) devices | I/O devices transfer information into and out of the computer.
Such a device could be a terminal and keyboard, a disk drive, or
a printer.  | 
| Memory | Physical (or main) memory is the amount of random access
memory (RAM) on the system.  | 
Chapter 13, Monitoring System Performance (Tasks) describes the tools that display statistics about the system's activity and performance.