at the command line without any arguments. The program will then generate a whole screen display with a listing of the current processes, which is constantly updated. The list is by default sorted according to how much CPU cycles the processes are using. At the top of the screen are statistics of CPU and memory usage, as well as the number of users and how long the system has been up.
With the top utility running, you can now change the format of the display and the ordering of the processes with simple key strokes. For example, if you hit "M" (capital m) the processes will be sorted by memory usage. Hitting "P" will list the processes by CPU usage.
The "1" (one) key will switch the display to showing statistics for each processor or core separately. Hitting the "1" (one) key again will switch back to a one line summary.
The "F" key will display a screen for choosing the sorting parameter.
Entering the question mark "?" gives you a list of all available functions.
You can use the ps command to show all processes on the system.