Section 9: The Index Register; Direct Index Register Functions - HP -11C Owner's Handbook Manual

126 Section 8: Subroutines
Key in the following set of variables:
x= 43, y=7.9, 2=13, t=8.0
Keystrokes Display
8 8.0000
1.3 1.3000
7.9(ENTER}4.3(0(A) 12.1074
"~~ ~
at SP A ta A NS
Section 9
The Index Register
The Index Register In Brief
The Index register (Rj) is one of the most powerful programming
tools available on your HP-11C. In addition to simple storage and
recall of data, the Index register can also be used for:
a
« Program loop counter and control functions.
« Indirectly addressing data storage registers, branches, and.
subroutines.
Index register control of loops and indirect addressing is performed.
using a control number you place in the Index register itself. The
integer portion of the control number determines the result of each
loop iteration or indirect addressing operation. The decimal portion.
of the control number contains the parameters for altering and
limiting the integer portion.
{0 and {(j) Abbreviated Key Sequences. The calculator is
designed so that you can omit the [f] prefix key in {1] or [{)] key
sequences. Even when the [f] prefix key is pressed in an [iJor [{i)) key
sequence, the calculator will automatically exclude the code for [f].
Direct Index Register Functions
Direct Index register functions act on the contents of the Index
register itself.
Index Register Store and Recall. (STO)[1) (store in R,) and [RCL
{1 (recall from Ry) operate in the same way as [STO] and [RCL}
operate with data storage registers Ry through Ry and Ro through
BR.
Exchanging X and I. Pressing [f][x=!] exchanges the contents of
the displayed X-register and the Index register in the same way
that pressing [x=,] exchanges the contents of the displayed X-
register and the Y-register.
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