The In-Out Register is the main path of communication with external
equipment. It is also part of the Arithmetic Element. In multiplication
it ends with the low order digits of the product. In division it starts
with the low order parts of the dividend and ends with the quotient.
The In-Out Register has a full set of shifting properties, (arithmetic
and logical).
* * * * *
There are three registers of 15 bit length which deal exclusively with
addresses. The design allows for expansion to 18 bits. These registers
are: