Is a switch that turns on the `interactive' mode. When this mode is on, you have an option to abort program execution, change the verbosity, turn on the work array debug switch WKP= , or sometimes to change a value of a single variable that may be passed to query. There is also the option to turn off the interactive mode. At the prompt, enter either a simple carriage return, or one of the following: `Vnnn', where nnn is the new verbosity; `W' to toggle printing of work array; `I' to turn off interactive prompt; `A' to abort program execution or, in the case when a variable is passed, you may also enter `Snnn', where nnn is a number (or T or F for logical variable); to change the value of that variable.