Anpassungen Path-Struktur

original/tools/builtInChips/ALU.hdl

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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: tools/builtInChips/ALU.hdl
+/**
+ * ALU (Arithmetic Logic Unit):
+ * Computes out = one of the following functions:
+ *                0, 1, -1,
+ *                x, y, !x, !y, -x, -y,
+ *                x + 1, y + 1, x - 1, y - 1,
+ *                x + y, x - y, y - x,
+ *                x & y, x | y
+ * on the 16-bit inputs x, y,
+ * according to the input bits zx, nx, zy, ny, f, no.
+ * In addition, computes the output bits:
+ * zr = (out == 0, 1, 0)
+ * ng = (out < 0,  1, 0)
+ */
+// Implementation: Manipulates the x and y inputs
+// and operates on the resulting values, as follows:
+// if (zx == 1) sets x = 0        // 16-bit constant
+// if (nx == 1) sets x = !x       // bitwise not
+// if (zy == 1) sets y = 0        // 16-bit constant
+// if (ny == 1) sets y = !y       // bitwise not
+// if (f == 1)  sets out = x + y  // integer 2's complement addition
+// if (f == 0)  sets out = x & y  // bitwise and
+// if (no == 1) sets out = !out   // bitwise not
+
+CHIP ALU {
+
+    IN  // 16-bit inputs:
+        x[16], y[16],
+        // Control bits:
+        zx, // Zero the x input
+        nx, // Negate the x input
+        zy, // Zero the y input
+        ny, // Negate the y input
+        f,  // Function code: 1 for add, 0 for and
+        no; // Negate the out output
+
+    OUT // 16-bit output
+        out[16],
+
+        // ALU output flags
+        zr, // 1 if out=0, 0 otherwise
+        ng; // 1 if out<0, 0 otherwise
+
+    BUILTIN ALU;
+}