HP 35s Instruction Manual page 2

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HP 35s Using Calculator Memories to Help Solve Problems
Variables and Memory Registers
When an equation is typed on the HP 35s, it can use variables with names from A through Z. For example an equation
has the variables X and A in it.
Variables can also be used in programs and in calculations from the keyboard.
Each variable consists of a number and of a place in the calculator memory where the number is stored.
The number is called the value of the variable. If no value has been give to a variable then its value is 0.
The place in memory where this number is stored is called a data register, or a memory register, or just a memory.
Each memory register can be referred to by a numeral as well as by its name. Register A is -1 and register Z is -26. Six
more registers can be referred to by numerals and hold values from statistics calculations. Two of the lettered variables
are special "index" registers, which are explained in another training aid. The names "data register" or "memory register"
or "memory" refer to all of these, not just the variables, so these names are often used in this training aid, rather than the
name "variables."
In many cases it is helpful to use variable names as mnemonics, for example D for density or P for pressure, but when
registers are used to store a table then names are meaningless and the numeral for each register is what counts.
This training aid shows ways in which memory registers can be used. A separate training aid covers the special topic of
how arithmetic can be carried out directly in memory registers and using the memory registers.
Practice Example: Storing and Using a Constant
The HP 35s provides a set of physical constants, such as the speed of light. The conversion functions also provide
constants to convert between metric and imperial measurements. Users who need to store other constants can put them
into the memory registers so they can be easily used in calculations.
Example 1: An engineer is working with a type of concrete that has a density of 149.8 lb/ft³ (Different types of concrete
have different densities, so the density of concrete is not a physical constant provided by the HP 35s!)
Store the density of this concrete in a data register and use it to calculate the mass of a concrete beam 2 ft
by 1.5 ft by 20ft.
Solution: Type the density, then press º
register. To store a density of 149.8 in variable D, press these keys.
When º
next key pressed should be one of the keys with letters A to Z at their lower right, and that the
corresponding letter will be used. For the letter "D", press the 9 key.
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3X² - 5X= A
and a variable name to store the density in that variable's memory
º
is pressed, the symbol "A..Z" appears at the top of the screen. This tells the user that the
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