4-bit ripple-carry adder
x0
y0
x1
y1
x2
y2
x3
y3
c
sum(x0,
y0, c)
sum(x1,
y1, carry(x0, y0, c))
sum(x2,
y2, carry(x1, y1, carry(x0,
y0, c)))
sum(x3,
y3, carry (x2, y2, carry(x1,
y1, carry(x0, y0, c))))
carry(x3,
y3, carry (x2, y2, carry(x1,
y1, carry(x0, y0, c))))
Note: There are
other ways to implement this.