Add solutions for part 1

projects/04/fill/Fill.asm

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+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/04/Fill.asm
+
+// Runs an infinite loop that listens to the keyboard input.
+// When a key is pressed (any key), the program blackens the screen,
+// i.e. writes "black" in every pixel;
+// the screen should remain fully black as long as the key is pressed.
+// When no key is pressed, the program clears the screen, i.e. writes
+// "white" in every pixel;
+// the screen should remain fully clear as long as no key is pressed.
+
+// Put your code here.
+
+  // const_num_screen_words = 32 * 256 = 8192
+  @8192
+  D = A
+  @const_num_screen_words
+  M = D
+
+  // pixel_value = 0
+  @pixel_value
+  M = 0
+
+(MAINLOOP)
+  // if RAM[KBD] == 0:
+  //   pixel_value = 0
+  // else:
+  //   pixel_value = -1
+  @KBD
+  D = M
+  @IF_TRUE
+  D;JEQ
+  @IF_FALSE
+  D;JMP
+
+  (IF_TRUE)
+    @pixel_value
+    M = 0
+    @END_IF
+    0;JMP
+  (IF_FALSE)
+    @pixel_value
+    M = -1
+  (END_IF)
+
+  @BLACKSCREEN
+  0;JMP
+
+
+(BLACKSCREEN)
+  // i = 0
+  @i
+  M = 0
+
+  // current_word = 0
+  @current_word
+  M = 0
+
+  // while i < const_num_screen_words
+  (BLACKSCREEN_LOOP)
+    // if (i - const_num_screen_words >= 0) goto BLACKSCREEN_LOOP_END
+    @i
+    D = M
+    @const_num_screen_words
+    D = D - M
+    @BLACKSCREEN_LOOP_END
+    D;JGE
+
+    // current_word = SCREEN + 1
+    @i
+    D = M
+    @SCREEN
+    D = D + A
+    @current_word
+    M = D
+
+    // RAM[current_word] = pixel_value
+    @pixel_value
+    D = M
+    @current_word
+    A = M
+    M = D
+
+    // i++
+    @i
+    M = M + 1
+
+    // goto BLACKSCREEN_LOOP
+    @BLACKSCREEN_LOOP
+    0;JMP
+  (BLACKSCREEN_LOOP_END)
+
+  // goto MAINLOOP
+  @MAINLOOP
+  0;JMP

projects/04/fill/Fill.hack

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+0000000000010000
+1110101010001000
+0010000000000000
+1110110000010000
+0000000000010001
+1110001100001000
+0110000000000000
+1111110000010000
+0000000000010000
+1110001100000101
+0000000000001100
+1110001100000010
+0000000000010010
+1110101010001000
+0000000000010010
+1110101010000111
+0000000000010010
+1110111010001000
+0000000000010000
+1111110000010000
+0000000000010001
+1111010011010000
+0000000000000000
+1110001100000010
+0100000000000000
+1110110000010000
+0000000000010000
+1111000010010000
+0000000000010011
+1110001100001000
+0000000000010010
+1111110000010000
+0000000000010011
+1111110000100000
+1110001100001000
+0000000000010000
+1111110111001000
+0000000000010010
+1110101010000111

projects/04/fill/Fill.tst

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+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/04/fill/Fill.tst
+
+load Fill.hack;
+echo "Make sure that 'No Animation' is selected. Then, select the keyboard, press any key for some time, and inspect the screen.";
+
+repeat {
+  ticktock;
+}

projects/04/fill/FillAutomatic.cmp

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+|RAM[16384]|RAM[17648]|RAM[18349]|RAM[19444]|RAM[20771]|RAM[21031]|RAM[22596]|RAM[23754]|RAM[24575]|
+|       0  |       0  |       0  |       0  |       0  |       0  |       0  |       0  |       0  |
+|      -1  |      -1  |      -1  |      -1  |      -1  |      -1  |      -1  |      -1  |      -1  |
+|       0  |       0  |       0  |       0  |       0  |       0  |       0  |       0  |       0  |

projects/04/fill/FillAutomatic.out

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+|RAM[16384]|RAM[17648]|RAM[18349]|RAM[19444]|RAM[20771]|RAM[21031]|RAM[22596]|RAM[23754]|RAM[24575]|
+|       0  |       0  |       0  |       0  |       0  |       0  |       0  |       0  |       0  |
+|      -1  |      -1  |      -1  |      -1  |      -1  |      -1  |      -1  |      -1  |      -1  |
+|       0  |       0  |       0  |       0  |       0  |       0  |       0  |       0  |       0  |

projects/04/fill/FillAutomatic.tst

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+// This file is part of www.nand2tetris.org
+// and the book "The Elements of Computing Systems"
+// by Nisan and Schocken, MIT Press.
+// File name: projects/04/fill/FillAutomatic
+
+// This script can be used to test the Fill program automatically, 
+// rather than interactively. Specifically, the script sets the keyboard
+// memory map (RAM[24576]) to 0, 1, and then again to 0. This simulates the 
+// acts of leaving the keyboard untouched, pressing some key, and then releasing
+// the key. After each on of these simulated events, the script outputs the values
+// of some selected registers from the screen memory map (RAM[16384]-RAM[24576]).
+// This is done in order to test that these registers are set to 000...0 or 111....1, 
+// as mandated by how the Fill program should react to the keyboard events.
+
+load Fill.hack,
+output-file FillAutomatic.out,
+compare-to FillAutomatic.cmp,
+output-list RAM[16384]%D2.6.2 RAM[17648]%D2.6.2 RAM[18349]%D2.6.2 RAM[19444]%D2.6.2 RAM[20771]%D2.6.2 RAM[21031]%D2.6.2 RAM[22596]%D2.6.2 RAM[23754]%D2.6.2 RAM[24575]%D2.6.2;
+
+set RAM[24576] 0,    // the keyboard is untouched
+repeat 1000000 {
+  ticktock;
+}
+output;              // test that the screen is white
+
+set RAM[24576] 1,    // a keyboard key is pressed
+repeat 1000000 {
+  ticktock;
+}
+output;              // test that the screen is black
+
+set RAM[24576] 0,    // they keyboard in untouched
+repeat 1000000 {
+  ticktock;
+}
+output;              // test that the screen is white
+