By default variables retain their value when the application is stopped and later restarted. However, variables can be given an initial value and then the value will be set to the initial value each time the application is started.
Variables can also be declared as being constant. A constant variable may not be changed at run-time and is shown with a blue frame.
Variables may have an associated update expression. In this case the variable automatically receives a new value in the beginning of every scan cycle.