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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/11/ConvertToBin/Main.jack
/**
* Unpacks a 16-bit number into its binary representation:
* Takes the 16-bit number stored in RAM[8000] and stores its individual
* bits in RAM[8001..8016] (each location will contain 0 or 1).
* Before the conversion, RAM[8001]..RAM[8016] are initialized to -1.
*
* The program should be tested as follows:
* 1) Load the program into the supplied VM emulator
* 2) Put some value in RAM[8000]
* 3) Switch to "no animation"
* 4) Run the program (give it enough time to run)
* 5) Stop the program
* 6) Check that RAM[8001]..RAM[8016] contains the correct binary result, and
* that none of these memory locations contains -1.
*/
class Main {
/**
* Initializes RAM[8001]..RAM[8016] to -1,
* and converts the value in RAM[8000] to binary.
*/
function void main() {
var int value;
do Main.fillMemory(8001, 16, -1); // sets RAM[8001]..RAM[8016] to -1
let value = Memory.peek(8000); // reads a value from RAM[8000]
do Main.convert(value); // performs the conversion
return;
}
/** Converts the given decimal value to binary, and puts
* the resulting bits in RAM[8001]..RAM[8016]. */
function void convert(int value) {
var int mask, position;
var boolean loop;
let loop = true;
while (loop) {
let position = position + 1;
let mask = Main.nextMask(mask);
if (~(position > 16)) {
if (~((value & mask) = 0)) {
do Memory.poke(8000 + position, 1);
}
else {
do Memory.poke(8000 + position, 0);
}
}
else {
let loop = false;
}
}
return;
}
/** Returns the next mask (the mask that should follow the given mask). */
function int nextMask(int mask) {
if (mask = 0) {
return 1;
}
else {
return mask * 2;
}
}
/** Fills 'length' consecutive memory locations with 'value',
* starting at 'startAddress'. */
function void fillMemory(int startAddress, int length, int value) {
while (length > 0) {
do Memory.poke(startAddress, value);
let length = length - 1;
let startAddress = startAddress + 1;
}
return;
}
}
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