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.
// TODO: optimize better in the future
(SET_SCREEN_PTR)
// R0 = SCREEN pointer
@SCREEN
D=A
@R0
M=D
// TODO: fix infinitely incrementing screen pointer bug
// end of screen: 0x5fff (dec 24575)
(IS_KEYPRESSED)
// if R0 == 24575; goto SET_SCREEN_PTR
@R0
D=M
@24575
D=D-A
@SET_SCREEN_PTR
D;JEQ
// D=KBD, goto WHITE_SCREEN if D == 0
@KBD
D=M
@WHITE_SCREEN
D;JEQ
(BLACK_SCREEN)
// *R0 = -1
@R0
A=M
M=-1
// ++R0
@R0
M=M+1
@IS_KEYPRESSED
0;JMP
// TODO: replace with D;JLT or something
(WHITE_SCREEN)
// *R0 = 0
@R0
A=M
M=0
// ++R0
@R0
M=M+1
@IS_KEYPRESSED
0;JMP
// TODO: replace with D;JLT or something
(END)
@END
0;JMP
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