What is another name for a serial in/ serial out register?

• A. Shift register
• B. Counter
• C. Decoder
• D. Multiplexer

Answer: (A)

A serial in/serial out register is fundamentally a shift register. In a shift register, data is fed in one bit at a time and, with each clock edge, all bits shift one position along the storage elements. The bit that was in the input ends up moving through the chain and exits at the serial output after being shifted through the register. This bit-by-bit movement is exactly what “serial in/serial out” describes.

This differs from the other devices: a counter increments a binary value on each clock, not a chain of bits moving through storage; a decoder selects one output line based on the input code; a multiplexer routes one of several inputs to the output. None of those inherently store and move a data stream through a sequence of storage elements the way a shift register does.