hw3.md

3

1.HalfAdder

/**
 * Computes the sum of two bits.
 */

CHIP HalfAdder {
    IN a, b;    // 1-bit inputs
    OUT sum,    // Right bit of a + b 
        carry;  // Left bit of a + b

    PARTS:
    // Put you code here:
    Xor(a=a,b=b,out=sum);
    And(a=a,b=b,out=carry);
}

2.FullAdder

/**
 * Computes the sum of three bits.
 */

CHIP FullAdder {
    IN a, b, c;  // 1-bit inputs
    OUT sum,     // Right bit of a + b + c
        carry;   // Left bit of a + b + c

    PARTS:
    // Put you code here:
    HalfAdder(a=a,b=b,sum=outs,carry=outc0);
    HalfAdder(a=c,b=outs,sum=sum,carry=outc1);
    Or(a=outc0,b=outc1,out=carry);
}

3.Adder16

/**
 * Adds two 16-bit values.
 * The most significant carry bit is ignored.
 */

CHIP Add16 {
    IN a[16], b[16];
    OUT out[16];

    PARTS:
   // Put you code here:
    FullAdder(a=a[0], b=b[0], c=false, sum=out[0], carry=carry1);
    FullAdder(a=a[1], b=b[1], c=carry1, sum=out[1], carry=carry2);
	FullAdder(a=a[2], b=b[2], c=carry2, sum=out[2], carry=carry3);
	FullAdder(a=a[3], b=b[3], c=carry3, sum=out[3], carry=carry4);
	FullAdder(a=a[4], b=b[4], c=carry4, sum=out[4], carry=carry5);
	FullAdder(a=a[5], b=b[5], c=carry5, sum=out[5], carry=carry6);
	FullAdder(a=a[6], b=b[6], c=carry6, sum=out[6], carry=carry7);
	FullAdder(a=a[7], b=b[7], c=carry7, sum=out[7], carry=carry8);
	FullAdder(a=a[8], b=b[8], c=carry8, sum=out[8], carry=carry9);
	FullAdder(a=a[9], b=b[9], c=carry9, sum=out[9], carry=carry10);
	FullAdder(a=a[10], b=b[10], c=carry10, sum=out[10], carry=carry11);
	FullAdder(a=a[11], b=b[11], c=carry11, sum=out[11], carry=carry12);
	FullAdder(a=a[12], b=b[12], c=carry12, sum=out[12], carry=carry13);
	FullAdder(a=a[13], b=b[13], c=carry13, sum=out[13], carry=carry14);
	FullAdder(a=a[14], b=b[14], c=carry14, sum=out[14], carry=carry15);
	FullAdder(a=a[15], b=b[15], c=carry15, sum=out[15], carry=carry16);
}

4.Inc16

/**
 * 16-bit incrementer:
 * out = in + 1 (arithmetic addition)
 */

CHIP Inc16 {
    IN in[16];
    OUT out[16];

    PARTS:
   // Put you code here:
    HalfAdder(a=in[0],b=true,sum=out[0],carry=carry1);
    HalfAdder(a=in[1],b=carry1,sum=out[1],carry=carry2);
    HalfAdder(a=in[2],b=carry2,sum=out[2],carry=carry3);
    HalfAdder(a=in[3],b=carry3,sum=out[3],carry=carry4);
    HalfAdder(a=in[4],b=carry4,sum=out[4],carry=carry5);
    HalfAdder(a=in[5],b=carry5,sum=out[5],carry=carry6);
    HalfAdder(a=in[6],b=carry6,sum=out[6],carry=carry7);
    HalfAdder(a=in[7],b=carry7,sum=out[7],carry=carry8);
    HalfAdder(a=in[8],b=carry8,sum=out[8],carry=carry9);
    HalfAdder(a=in[9],b=carry9,sum=out[9],carry=carry10);
    HalfAdder(a=in[10],b=carry10,sum=out[10],carry=carry11);
    HalfAdder(a=in[11],b=carry11,sum=out[11],carry=carry12);
    HalfAdder(a=in[12],b=carry12,sum=out[12],carry=carry13);
    HalfAdder(a=in[13],b=carry13,sum=out[13],carry=carry14);
    HalfAdder(a=in[14],b=carry14,sum=out[14],carry=carry15);
    HalfAdder(a=in[15],b=carry15,sum=out[15]);
}