To enter n bits of data in a serial in serial out shift register, the number of clock pulses required are:

SISO:

In a n-bit shift register, to enter n bits of data n clock pulses are required

However, to output data serially (n-1) clock pulses are required

SIPO:

For n bit serial input data, n clock pulses are required

To output data no clock pulse is required

PISO:

To store n bit data – 1 clock pulse required

To output data (n-1) clock pulses are required

PIPO:

1 clock pulse is required no input data

No clock pulse is required to output data