Interact with the keyboard

Currently, text can be accepted from the user during program execution mainly via 3 primitives: key?, readchar and read.

key?: is read as true or false according to whether a key has been pressed or not since the start of program execution.

readchar:

• If key? is false, the program is paused until the user presses a key.
• If key? is true, it gives the key which was pressed last. These are the values given for particular keys:
  
  

  Table: Values for particular keys

  A --> 65	B --> 66	C --> 67	etc ...	Z --> 90
  $\leftarrow$ --> -37 or -226 (NumPad)	$\uparrow$ --> -38 or -224	$\rightarrow$ --> -39 or -227	$\downarrow$ --> -40 or -225
  Echap --> 27	F1 --> -112	F2 --> -113	....	F12 --> -123
  Shift --> -16	Espace --> 32	Ctrl --> -17	Enter --> 10

  
  

If you are uncertain about the value returned by a key, you can type:
pr readchar. The interpreter will then wait for you to type on a key before giving you the corresponding value.

read list_title word: Presents a dialogue box whose title is list_title. The user can then input a response in a text field, and the response will be stored in the form of a word or a list (if the user wrote several words) in the variable :word, and will be evaluated when the OK button is pressed.