code: function onRead (key) {
    if (key !== null) {
      if (cli.debug) console.log('Key:', key)
      // Exits on CTRL-C
      if (key === '\u0003') process.exit()
      // If enter is pressed and the program is waiting for the user to press enter
      // so that the emulator can step forward, then call the appropriate callback
      if (key.charCodeAt(0) === 13 && readingFn() && onReadCb) onReadCb(key.charCodeAt(0))
      else if (cpu) {
        // Since the CPU is initialized and the program is not waiting for the user
        // to press enter, pass the pressed key to the LC-2 CPU Console.
        cpu.console.input(key)
      }
      readingFn(false)
    }
  }
docs: This function processes an input key from STDIN.