A shift register which can shift the data in only one direction is called a unidirectional shift register. A shift register which can shift the data in both the directions is called as a bidirectional shift register.

A shift register is capable of performing the following operations:

1. Parallel loading (parallel input-parallel output)
2. Left shifting
3. Right shifting

The mode control input is connected to logic 1 for parallel loading operation whereas it is connected to 0 for serial shifting. With mode control pin connected to ground, the universal shift register acts as a bidirectional register. For serial left operation, the input is applied to the serial input which goes to AND gate-1. For the shift right operation the serial input is applied to 'D' input (Input of AND gate 8)