INPUT : Prompts user to input into a variable with a "?" prompt without any
preceeding text or displays some preceeding text followed by
the "?" prompt.
syntax: INPUT <variable> or
INPUT "<string>",<variable>
INPUT with <variable> prompts "?" during execution. Enter a value
(which can be an expression) and press or click [enter]. The value is evaluated
and stored to <variable>, and the program resumes execution. You can display a
preceeding string as a prompt in which case the preceeding string is displayed
before the "?" prompt. Enter a value and press [Enter]. The value is stored
to <variable>, and the program resumes execution.