HP 15c Scientific manual Memory Allocation, Memory Space, Appendix C, Registers, 213

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 67 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: RI, R0, and R1.

∙The common pool contains uncommitted registers available for allocation to programming, matrices, the imaginary stack, and _and foperation. At power-up there are 46 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.

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