HP 15c Collector's Edition

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Appendix C
Memory Allocation
The Memory Space
Storage registers, program lines, and advanced function execution
*
all
draw on a common memory space in the HP 15c. The availability of
memory for a specific purpose depends on the current allocation of
memory, as well as on the total memory capacity of the calculator.
Registers
Memory space in the HP 15c is allocated on the basis of registers. This
space is partitioned into two pools, which strictly define how a register
may be used. There is always a combined total of 99 registers in these two
pools.
 The data storage pool contains registers which may be used only
for data storage. At power-up (Continuous Memory reset) this
equals 21 registers. This pool contains at least three registers at all
times: R
I
, R
0
, and R
1
.
 The common pool contains uncommitted registers available for
allocation to programming, matrices, the imaginary stack, and
_ and f operation. At power-up there are 78 uncommitted
registers in the common pool.
*
The use of _, f, Complex mode, or matrices temporarily requires extra memory
space, as explained later in this appendix.