Page 19 - Appplied Mathematics for the Petroleum and Other Industries, 5th Edition

40 THE CALCULATOR

CHOOSING A CALCULATOR

Calculators are available in a wide variety of capabilities and prices. The least
expensive models not only perform addition, subtraction, multiplication, and
division, but also percentages and square roots. Most also have a memory. The
user can store a set of numbers in the calculator’s memory and retrieve it later
without having to reenter the numbers.
For example, suppose you need to convert several measurements in feet to
metres. To convert feet to metres, you multiply the number of feet by 0.3048.
By entering 0.3048 into the calculator’s memory, you may recall this conversion
factor by pressing a single key rather than entering 0.3048 each time you wish
to make the conversion. Also, when solving complicated equations, you can store
part of the solved equation in the calculator’s memory. Then, you can retrieve
the partial solution later when it is required to solve the entire problem. Later,
this chapter covers both these uses of a calculator’s memory.
More expensive models offer trigonometric and logarithmic functions,
among other things. Also, advanced models are equipped with more than one
level of memory. That is, you can store parts of a calculation in more than one
place. Although this chapter does not cover it because programming is beyond
the scope of this manual, some calculators are programmable: you can load
special mathematical operations into the calculator, which allow it to perform
advanced functions.

Calculator Features

When choosing a calculator, it is important to match your calculation needs with
the calculator’s capabilities. If you anticipate solving involved calculations, then
consider buying a sophisticated model. On the other hand, if most calculations
are little more than solving addition, subtraction, multiplication, and division
problems, then a simple, inexpensive model is adequate.
Most of today’s handheld calculators are battery operated or have a power
cell that operates the calculator when it is struck by light. Manufacturers often
call such calculators solar powered, but sunlight is not needed to operate them.
Ordinary indoor or outdoor light is adequate. If batteries operate the calculator,
it may come with an AC adapter-charger, which not only powers the calculator,
but also charges the batteries when the calculator is plugged in. Desktop calcula-
tors may plug into a normal electrical outlet.
Keyboards have the usual operational symbols of +, –, ×, ÷, and =. Advanced
2
models contain other symbols, such as %, √, x , y , log, and sin. (This chapter
x
discusses these keys shortly.) The keyboard also has a period key (.), which is a
decimal point. The number of symbols and characters vary with the complexity
and price of the calculator. The manufacturer may print the numbers and sym-
bols directly on the keys, on the case near the keys, or on both. In this chapter,
Petroleum Extension-The University of Texas at Austin
reference to a key is by its symbol regardless of its printed location. Figure 2.1
shows typical calculator keyboards.
Small calculators display numbers and other entries in a window usually
located at the top of the calculator. Light emitting diodes (LEDs) or liquid
crystal displays (LCDs) show the numbers and symbols in the window. (Some
desktop calculators also print out characters on a paper tape.) The display should
be easy to read—that is, the size, color, intensity, and visibility of the symbols and
numbers should be readable in sunlight as well as in artificial light.