Design a 4-bit register that can accept an input from the user and store the accepted input. The 4-bit register will operate in two modes: 1) the data input is stored into the register, and 2) The register retains its past value and does not store the new value. To operate in these two states, the register should accept 5 inputs: 4 data inputs and 1 control input. If the control input is 0, the input is stored. Otherwise, the input is not stored.