HP 15c Scientific manual Index Register Loop Control, V and % Keys, 106

Section 10

The Index Register

and Loop Control

The Index register (RI) is a powerful tool in advanced programming of the HP-15C. In addition to storage and recall of data the Index register can use an index number to:

∙Count and control loops.

∙Indirectly address storage registers, including those beyond R.9 (R19).

∙Indirectly branch to program line numbers, as well as to labels.

∙Indirectly control the display format.

∙Indirectly control flag operations.

The V and % Keys

Direct Versus Indirect Data Storage With the Index Register

The Index register is a data storage register that can be used directly, with V, or indirectly, with %.* The difference is important to note:

V		%
The V function uses the	The % function uses the absolute
number itself in the Index	value of the integer portion of the
register.	number in the Index register to
	address	another	data	storage
	register.	This is	called	indirect
	addressing.

*Note that the matrix functions and complex functions use the V and % keys also, but for different purposes. Refer to sections 11 and 12 for their usage.

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