All APL variables are double precision floating-point values. You can use variables for calculations or to define the interaction between the adventure driver (Advdrv.dll) and Flight Simulator.
You can use user variables to save the results of calculations. The variables A–Z are predefined; but you can create new variables using the Declare <variable name> command. String variables can be declared using Declare <variable name> = "initial value" and can be referenced in the Print, Scroll, and Debug_Print commands.
The main interface between APL and Flight Simulator is through Flight Simulator variables. Flight Simulator variables can be referenced and, in some cases, changed by the APL program as though they were normal variables, but when their values are referenced, they actually call an interface function. Generally, the interface function reads the value of the actual Flight Simulator internal variable associated with the APL variable, performs any appropriate scaling, range conversion, or other translation, and converts the result to a double precision floating-point value. The interface function also performs any other functions, as necessary. For example, when a value is written to the variable, the interface function performs any necessary range checking and then updates the actual value in Flight Simulator or calls the appropriate interface function. The interface function does not have to have any connection with Flight Simulator; for example, Random is implemented in this way. For details on Flight Simulator variables, see the Flight Simulator Variables Available to APL section in Help.