83 lines
2.6 KiB
Plaintext
83 lines
2.6 KiB
Plaintext
|
// 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;
|
||
|
|
}
|
||
|
|
}
|