week4.md

ALU

    IN  
        x[16], y[16],  // 16-bit inputs        
        zx, // zero the x input?
        nx, // negate the x input?
        zy, // zero the y input?
        ny, // negate the y input?
        f,  // compute out = x + y (if 1) or x & y (if 0)
        no; // negate the out output?

    OUT 
        out[16], // 16-bit output
        zr, // 1 if (out == 0), 0 otherwise
        ng; // 1 if (out < 0),  0 otherwise

    PARTS:
   // Put you code here:
   Mux16(a=x, b=false, sel=zx, out=zxo);
   Not16(in=zxo, out=nzxo);
   Mux16(a=zxo, b=nzxo, sel=nx, out=nxo);

   Mux16(a=y, b=false, sel=zy, out=zyo);
   Not16(in=zyo, out=nzyo);
   Mux16(a=zyo, b=nzyo, sel=ny, out=nyo);

   And16(a=nxo, b=nyo, out=nnand);
   Add16(a=nxo, b=nyo, out=nnadd);

   Mux16(a=nnand, b=nnadd, sel=f, out=fo);
   Not16(in=fo, out=nfo);
   Mux16(a=fo, b=nfo, sel=no, out=noo, out[0..7]=oo1, out[8..15]=oo2);

   Or8Way(in=oo1, out=oout1);
   Or8Way(in=oo2, out=oout2);
   Or(a=oout1, b=oout2, out=nzr);
   Not(in=nzr, out=zr);

   And16(a[0..15]=true, b=noo, out[15]=ng, out[0..14]=drop);

   Or16(a=noo,b=false, out=out); //noo=output}