Question 1: Assume you are required to design a logic circuit enclosed in a black box to detect a password, which can be changed by an authorized administrator any time. The password is composed
of a squence of a 4-bit decimal number, i. e., each bit is in the range 'O' to '9' and sent in BCD format.
As stated above, the password should be suitable to change any time, i. e., while the initial password
can be "0120", it can also be replaced by "3456" any time by the administrator. In this design, you are
allowed to use only 4-bit parallel output shift-registers with a single-serial input data line and 4-bit
magnitude comparators. The password to detect is "1234".