{ xTurtle Tutorial Example #3: I/O

  I/O, or Input/Output, refers to
  the exchange of information 
  between a program and the person
  using the program.  All the 
  turtle graphics commands, 
  including DrawText, are examples
  of output (from the computer
  to the user).  This file
  gives examples of several other
  I/O commands in xTurtle.
}

TellUser("Hello World!")
   { This command pops up a box
     displaying the specified
     string to the user.  The
     user must click on a 
     displayed OK button before
     the program can continue. }
     
DECLARE amount

AskUser("What is the amount?", amount)
   { This also pops up a box 
     displaying the string.
     There is also an input box
     where the user can type in 
     a number.  That number 
     is stored as the value of 
     the specified variable.
     In this example, the number
     typed by the user is stored
     in the variable amount. }
     
amount := amount * 1.07
   { Uses the value typed in 
     by the user in a computation.
     The computed value is
     then stored as the new
     value of amount. }
     
TellUser("The amount is now #amount.")
   { Just as in DrawText, strings
     can include variables.  This
     command displays a string 
     containing the new value of
     amount. }
     
DECLARE resp

YesOrNo("Are you happy?", resp)
   { Displays the string, and
     gets a response from the user.
     With this command, the user
     can only answer yes or no.
     If the user says yes, the
     value of the variable is
     set to 1; if the user says
     no, the value is set to 0. }
     
TellUser("The recorded answer is #resp")