Shift registers

Can anyone supply an easy to understand explanation of how an A&B shift register works. Most shift registers have Data input, Clock input and Reset input.A&B has File,control,bit address and Length

THe 'Bit Address' is the bit that is being shifted into the bit array. The File is the array of bits to shift. The Control is a block of information used internally by the shift instructions to handle the shifting and report things like errors, position values, or done.
Length is the number of bits to shift.

All of this is very well documented in the online help in all AB Programming software.

This is not the equivilant of an IC based shift register, nor is it the equivilant of assembly language shift instructions, nor the derived higher level language shift instructions.

PLC shifts are Similar, but NOT the same.

This might help:
http://www.mrplc.com/kb/index.php?page=index_v2&id=71&c=12