// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: tools/builtIn/Keyboard.hdl

/**
 * The keyboard (memory map).
 * Outputs the code of the currently pressed key.
 *
 * The built-in chip implementation has two side effects supplied 
 * by the simulator. First, the keyboard memory map is continuously 
 * being refreshed from the physical keyboard unit. Second, it 
 * displays a keyboard icon and data entry GUI.
 */

CHIP Keyboard {

    OUT out[16];   // The ASCII code of the pressed key, 
                   // or 0 if no key is currently pressed, 
                   // or one the special codes listed in Figure 5.5.

    BUILTIN Keyboard;
}