diff options
| author | Yuchen Pei <me@ypei.me> | 2017-11-29 12:30:41 +0100 |
|---|---|---|
| committer | Yuchen Pei <me@ypei.me> | 2017-11-29 12:30:41 +0100 |
| commit | a000308104aab27c2dde9a306f1bc654b2db4806 (patch) | |
| tree | aecc628e14c1628b5714281437aba18680cdc27b /projects/11/ConvertToBin | |
first commit
Diffstat (limited to 'projects/11/ConvertToBin')
| -rw-r--r-- | projects/11/ConvertToBin/Main.jack | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/projects/11/ConvertToBin/Main.jack b/projects/11/ConvertToBin/Main.jack new file mode 100644 index 0000000..e627486 --- /dev/null +++ b/projects/11/ConvertToBin/Main.jack @@ -0,0 +1,82 @@ +// 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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