Section 10: The Index Register and Loop Control 107

Indirect Program Control With the Index Register

The V key is used for all forms of indirect program control other than indirect register addressing. Hence, V (not %) is used for indirect program branching, indirect display format control, and indirect flag control.

Program Loop Control

Program loop counting and control can be carried out in the HP-15C by any storage register: R0 through R9, R.0 through R.9, or the Index register (V). Loop control can also be carried out indirectly with %.

The Mechanics

Both V and % can be used in abbreviated key sequences, omitting the preceding ´prefix (as explained on page 78).

Index Register Storage and Recall

Direct. O V and l V. Storage and recall between the X- register and the Index register operate in the same manner as with other data storage registers (page 42).

Indirect. O(or l) %stores into (or recalls from) the data storage register whose number is addressed by the integer portion of the value (0 to 65) in the Index register. See the table below and on the next page.

Indirect Addressing

If RI contains:

%will address:

t Vor G Vwill

 

transfer to:*

 

 

 

 

 

 

± 0

R0

´b 0

 

 

9

R9

´b 9

10

R.0

"

"

.0

11

R.1

"

"

.1

 

 

19

R.9

´b.9

20

R20

"

"

A

*For RI ≥ 0 only.

(Continued on next page.)

Page 107
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HP 15c Scientific Indirect Program Control With the Index Register, Program Loop Control, Index Register and Loop Control