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Shift registers have a direction: a left shift register moves bits from right to left; a right shift register moves in the opposite direction. Usually, a shift register circuit is wired to work one way or the other, though bi-directional shift registers move bits right or left, depending on the state of a direction input. For example, a four-bit shift register may have the following contents:

0011

After two left shifts, the contents look like this:

1100

1. Serial In/Shift Left/Serial Out Operation Data is shifted in the left-hand direction one bit at a time with each transition of the clock signal.The data enters the shift register serially from the right hand side and after four clock transitions the 4-bit register has 4-bits of data. The data is shifted out serially one bit at a time from the left hand side of the register if clock signals are continuously applied.Thus after 8 clock signals the 4-bit data is completely shifted out of the shift register.

2. Serial In/Shift Right/Serial Out Operation Data is shifted in the right-hand direction one bit at a time with each transition of the clock signal. The data enters the shift register serially from the left hand side and after four clock transitions the 4-bit register has 4-bits of data. The data is shifted out serially one bit at a time from the right hand side of the register if clock signals are continuously applied. Thus after 8 clock signals the 4-bit data is completely shifted out of the shift register.