HP 15c Scientific Day, Day, Day, copy, (recall), 1,322.5000, 1,520.8750, 1,749.0063, (X exchange), lowest-numbered, registers available, exchanges the contents

42 Section 3: The Memory Stack, LAST X, and Data Storage

Keystrokes Display

*1,150.0000 Population at the end of day 1.

*	1,322.5000	Day 2.
*	1,520.8750	Day 3.
*	1,749.0063	Day 4.

Storage Register Operations

When numbers are stored or recalled, they are copied between the display (X-register) and the data storage registers. At ―power-up‖ (initial turn-on or Continuous Memory reset) the HP-15C has 21 directly accessible storage registers: R0 through R9, R.0 through R.9, and the Index register (RI) (see the diagram of the registers on the inside back cover). Six registers, R2 to R7, are also used for statistics calculations.

The number of available data storage registers can be increased or decreased. The m function, which is used to reallocate registers in calculator memory, is discussed in appendix C, Memory Allocation. The lowest-numbered registers are the last to be deallocated from data storage, therefore it is wisest to store data in the lowest-numbered registers available.

Storing and Recalling NumbersO(store). When followed by a storage register address (0 through 9 or

.0 through .9*), this function copies a number from the display (X-register) into the specified data storage register. It will replace any existing contents of that register.

l(recall). Similarly, you can recall data from a particular register into the display by pressing l followed by the register address. This brings a copy of the desired data into the display; the contents of the storage register remain unaltered.

X (X exchange). Followed by 0 through .9,* this function exchanges the contents of the X-register and the addressed data storage register. This is useful to view storage registers without disturbing the stack.

*All storage register operations can also be performed with the Index register (using Vor %), which is covered in section 10, and with matrices, section 12.