HP HP-67 - Page 236

232 Using the I-Register for Indirect Control
To recall numbers that are stored in any register, you can use the
(recall) key followed by the number or letter key of the register
address. (For secondary storage registers, use the function to
exchange contents of the primary and secondary registers before using
the function.) However, when the address currently stored in the
I-register is correct, you can recall the contents of a storage register
by simply pressing [@ (or (@). For example:
Press Display
5 Contents of storage
register R recalled to
displayed X-register.
(0] Since the I-register still
contains the number 12,
this operation recalls the
contents of the storage
register (secondary
register Rg,) addressed by
the number 12.
By changing the number in the I-register, you change the address
specified by or (@ . For example:
Press Display
20
@ Contents of storage
register Rg recalled to
5o displayed X-register.
1.23 Contents of storage
register Ry recalled to
displayed X-register.
Storage register arithmetic is performed upon the contents of the
register addressed by I by using Ei2) E3 (@, 8O, 80,
and & [@. Again, you can access any storage register, primary
or secondary—you never have to use the function when using
the I-register for addressing. For example:
Press Display
1
One
added
to
number
in
storage register (R;)
currently addressed by
the I-register.