Command Mode

When calling the program, you specify opions and then exactly one command.

The system executes this command and then ends the program.

Session Mode

First you just call the program, then you enter and execute commands in succession without the program being ended.

To exit session mode, you end the program.

Script Mode

When calling the program, you specify the name of a script file that contains the commands to be executed.

The program executes the script in the background.