Question

A serial in/parallel out, 4-bit shift register initially contains all 1s. The data nibble 0111 is waiting to enter. After four clock pulses, the register contains ________

(a) 0000

(b) 1111

(c) 0111

(d) 1000

The question was asked during a job interview.

My question is based upon Shift Registers in portion Registers of Digital Circuits

Answer 1

Right option is (c) 0111

For explanation: In Serial-In/Parallel-Out shift register, data will be shifted all at a time with every clock pulse. Therefore,

             Wait | Store

             0111 | 0000

       011 | 1000 1st clk

               01 | 1100 2nd clk

                0 | 1110 3rd clk

                X | 1111 4th clk.