KEY Statements (Assignment)
 ----------------------------------------------------------------------------


 Action

 Assign soft-key string values to function keys, then display the values and
 enable or disable the function-key display line.


 Syntax



  KEY  n%,  stringexpression$


  KEY ON

  KEY OFF
 KEY LIST


 Remarks


 The argument  n% is a number representing the function key. The values for
 n% are 1 to 10 for the function keys, and 30 and 31 for function keys F11
 and F12 on 101-key keyboards. The  stringexpression$ is a string of up to 15
 characters that is returned when the function key is pressed. If the
 stringexpression$ is longer than 15 characters, the extra characters are
 ignored.

 The  KEY statements allows you to designate special "soft-key" functions --
 strings that are returned when function keys are pressed.

 Assigning a null string to a soft key disables the function key as a soft
 key.

 If the function key number is not in the correct range, BASIC generates the
 error message Illegal function call, and the previous key string expression
 is retained.

 You can display soft keys with the  KEY ON,  KEY OFF, and  KEY LIST
 statements.

-----------------------------------------------------------------------------
 Statement                               Action
 ----------------------------------------------------------------------------
  KEY ON                                 Displays the first six characters
                                         of the soft-key string values on
                                         the bottom line of the screen.

  KEY OFF                                Erases the soft-key display from
                                         the bottom line, making that line
                                         available for program use. It does
                                         not disable the function keys.

  KEY LIST                               Displays all soft-key values on
                                         the screen, with all 15 characters
 Statement                               Action
 ----------------------------------------------------------------------------
                                         the screen, with all 15 characters
                                         of each key displayed.





 If a soft key is pressed, the effect is the same as if the user typed the
 string associated with the soft key.  INPUT$,  INPUT, and  INKEY$ all can be
 used to read the string produced by pressing the soft key.

 See Also

  ON  event; Appendix A, "Keyboard Scan Codes and ASCII Character Codes"


 Examples

 The following examples show how to assign values to soft keys. First is an
 example of assigning and disabling a soft key.  KEY LIST displays key values
 after KEY 4 has been assigned and again after it has been disabled.

 KEY 4, "MENU" + CHR$(13) ' Assigns to soft key 4 the string

 KEY LIST' "MENU" followed by a carriage return.

 KEY 4, ""  ' Disables soft key 4.

 KEY LIST

 This is an example of using  KEY statements to set up one-key equivalents of
 menu selections. For example, pressing the F1 key is the same as entering
 the string "Add".


 CLS                       ' Clear screen.

 DIM KeyText$(3)

 DATA Add, Delete, Quit

 ' Assign soft-key strings to F1 to F3.

 FOR I = 1 TO 3

    READ KeyText$(I)

    KEY I, KeyText$(I) + CHR$(13)   ' String followed by Enter.

 NEXT I



 ' Print menu.

 PRINT "                 Main Menu" . PRINT

 PRINT "           Add to list (F1)"

 PRINT "           Delete from list (F2)"

 PRINT "           Quit (F3)" . PRINT



 ' Get input and respond.

 DO

    LOCATE 7,1 . PRINT SPACE$(50);

    LOCATE 7,1 . INPUT "             Enter your choice.", R$

    SELECT CASE R$

       CASE "Add", "Delete"

          LOCATE 10,1 . PRINT SPACE$(15);

          LOCATE 10,1 . PRINT R$;

       CASE "Quit"

          EXIT DO

       CASE ELSE

          LOCATE 10,1 . PRINT "Enter first word or press key."

    END SELECT

 LOOP