Also, design a 4-bit shifter. The shifter should have four data input lines (D3, D2, D1, and D0), four data output lines (S3, S2, S1, and S0), and two control input lines (C1 and C0). Here's how S should depend on the values of D and C.
C1 C0 S3 S2 S1 S0 ============================ 0 0 D3 D2 D1 D0 0 1 0 D3 D2 D1 1 0 D2 D1 D0 0 1 1 D3 D2 D1 D0
That is, control values 0 and 3 say "no shift," 1 says "shift right,"
and 2 says "shift left."