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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/03/a/Bit.hdl
+
+/**
+ * 1-bit register:
+ * If load[t] == 1 then out[t+1] = in[t]
+ *                 else out does not change (out[t+1] = out[t])
+ */
+
+CHIP Bit {
+    IN in, load;
+    OUT out;
+
+    PARTS:
+    // Put your code here:
+}

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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/03/a/PC.hdl
+
+/**
+ * A 16-bit counter with load and reset control bits.
+ * if      (reset[t] == 1) out[t+1] = 0
+ * else if (load[t] == 1)  out[t+1] = in[t]
+ * else if (inc[t] == 1)   out[t+1] = out[t] + 1  (integer addition)
+ * else                    out[t+1] = out[t]
+ */
+
+CHIP PC {
+    IN in[16],load,inc,reset;
+    OUT out[16];
+
+    PARTS:
+    // Put your code here:
+}

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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/03/a/RAM64.hdl
+
+/**
+ * Memory of 64 registers, each 16 bit-wide. Out holds the value
+ * stored at the memory location specified by address. If load==1, then 
+ * the in value is loaded into the memory location specified by address 
+ * (the loaded value will be emitted to out from the next time step onward).
+ */
+
+CHIP RAM64 {
+    IN in[16], load, address[6];
+    OUT out[16];
+
+    PARTS:
+    // Put your code here:
+}

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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/03/a/RAM8.hdl
+
+/**
+ * Memory of 8 registers, each 16 bit-wide. Out holds the value
+ * stored at the memory location specified by address. If load==1, then 
+ * the in value is loaded into the memory location specified by address 
+ * (the loaded value will be emitted to out from the next time step onward).
+ */
+
+CHIP RAM8 {
+    IN in[16], load, address[3];
+    OUT out[16];
+
+    PARTS:
+    // Put your code here:
+}

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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/03/a/Register.hdl
+
+/**
+ * 16-bit register:
+ * If load[t] == 1 then out[t+1] = in[t]
+ * else out does not change
+ */
+
+CHIP Register {
+    IN in[16], load;
+    OUT out[16];
+
+    PARTS:
+    // Put your code here:
+}

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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/03/b/RAM16K.hdl
+
+/**
+ * Memory of 16K registers, each 16 bit-wide. Out holds the value
+ * stored at the memory location specified by address. If load==1, then 
+ * the in value is loaded into the memory location specified by address 
+ * (the loaded value will be emitted to out from the next time step onward).
+ */
+
+CHIP RAM16K {
+    IN in[16], load, address[14];
+    OUT out[16];
+
+    PARTS:
+    // Put your code here:
+}

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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/03/b/RAM4K.hdl
+
+/**
+ * Memory of 4K registers, each 16 bit-wide. Out holds the value
+ * stored at the memory location specified by address. If load==1, then 
+ * the in value is loaded into the memory location specified by address 
+ * (the loaded value will be emitted to out from the next time step onward).
+ */
+
+CHIP RAM4K {
+    IN in[16], load, address[12];
+    OUT out[16];
+
+    PARTS:
+    // Put your code here:
+}

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+// This file is part of the materials accompanying the book 
+// "The Elements of Computing Systems" by Nisan and Schocken, 
+// MIT Press. Book site: www.idc.ac.il/tecs
+// File name: projects/03/b/RAM512.hdl
+
+/**
+ * Memory of 512 registers, each 16 bit-wide. Out holds the value
+ * stored at the memory location specified by address. If load==1, then 
+ * the in value is loaded into the memory location specified by address 
+ * (the loaded value will be emitted to out from the next time step onward).
+ */
+
+CHIP RAM512 {
+    IN in[16], load, address[9];
+    OUT out[16];
+
+    PARTS:
+    // Put your code here:
+}