The program produces an ordered list of running processes selected by user-specified criteria, and updates it periodically.

Some versions of top allow extensive customization of the display, such as choice of columns or sorting method.

IBM AIX has an updating running processes list as part of the topas and topas_nmon commands.

The instant variations of the number of processes are damped with an exponential decay formula which is calculated using fixed point math.

[6] The ps program is similar to top, but instead produces a snapshot of processes taken at the time of invocation.

At complete utilization with no task switching, the load average is equal to the number of CPUs.