Reads a character from the keyboard.
 
INKEY$
 
    - INKEY$ returns a null string if there is no character to return.
    - For standard keys, INKEY$ returns a 1-byte string containing the
      character read.
    - For extended keys, INKEY$ returns a 2-byte string made up of the null
      character (ASCII 0) and the keyboard scan code.
 
Example:
    PRINT "Press Esc to exit..."
    DO
    LOOP UNTIL INKEY$ = CHR$(27)    '27 is the ASCII code for Esc.
 
See Also    <KEYBOARD SCAN CODES>