ASK: Prompt for Numerical Input at the Keyboard

Form: ASK ['An optional prompt in quotes'] var_name
This command can be used to request the input of variable values during the execution of a procedure. When the ASK command is executed, the prompt will be displayed at the terminal until the requested value is typed in. If no prompt is given, the command will respond with 'ENTER var_name:'. Only one value can be requested per ASK command.

Examples:

ASK BCKGND
will print 'ENTER BCKGND : on your screen. When you enter an expression and hit RETURN, the value of BCKGND will be set to the number you specified.

ASK 'Enter an estimate for the background >> '
BCKGND will type the prompt 'Enter an estimate for the background >> ' on your terminal, and wait for you to enter an expression; the value of BCKGND is the value of that expression.
Note that the reply to ASK can be any valid expression.