Indirect Index Register Functions - HP -11C Owner's Handbook Manual

130 Section 9: The Index Register
'Indirect Index Register Functions
Indirect Index register functions do not affect the contents of Rj.
Instead, they use the nnnnn (integer) portion of the number stored
in R; as an address for determining where in memory to execute the
function. Indirect functions are frequently used in conjunction
with or in programs when it is desirable to use the same
program instruction repeatedly to sequentially address storage
registers, branches, or subroutines.
Indirect Storage and Recall. ((i))) and ((i))* store or
recall numbers using the data storage register addressed by the
absolute value of nnnnn. For addressing R through Ry, nnnnn =
0 through 9; for R; through R4y, nnnnn = 10 through 19; for R,
nnnnn = 20. (Refer to the Indirect Addressing table on the
following page.)
Exchange X, Indirect. exchanges the contents of the
X-register with the contents of the storage register addressed by the
absolute value of nnnnn.
Indirect Storage Register Arithmetic. (STO]([+], (-], [x], or [2])
((i)) performs storage register arithmetic on the contents of the
storage register addressed by the absolute value of nnnnn.
Examples
If 5.01202 is stored in the Index register:
nnnnn=5 xxx=012 yy=02
(sTo](] = (sT0]5
(f)(x=()] = Exchange X-register and Rg Contents
(sTol(J@) = [sTol(+]5
Indirect Branching to Label or Line Number. In a running
program:
1. If nnnnnis = 0, (1] branches execution downward in
program memory to the next label specified by nnnnn.
* Refer to page 127, (1) and ((i)) Abbreviated Key Sequences.