December 1974 Popular Mechanics 
[Table of Contents]
Wax nostalgic about and learn from the history of early
mechanics and electronics. See articles from
Popular Mechanics,
published continuously since 1902. All copyrights hereby acknowledged.

Just as most people no
longer wear a wristwatch since their (practically) surgically attached
smartphones can provide the time, few people bother with carrying around an
electronic calculator. It's' been that way for at least a decade now. When this
article entitled "Calculators Get Smaller, Smarter and Cheaper" appeared in a
1974 issue of Popular Mechanics magazine, pocket electronic calculators
were still a relatively new phenomenon. Hewlett Packard had introduced
their first calculator, the HP−35, just two years earlier. The first Americanmade
pocket calculator, the
Bowmar 910B, aka "The Brain," came out in late 1971/early
1972 and sold for about $240. It had only basic math functions and sported a
tiny LED display. Prices fell very quickly as many companies were releasing
models with more and more features. By the time of this article, calculators
with basic functions could be bought for a mere $16.95 ($84.05 in 2019 money per
the
BLS CPI calculator). I got my first pocket calculator
sometime around 1975 or so; it was one my father brought home from work that a
client of his had given him. I don't recall the make or model number, but it was
really cool to own such a marvel of a device. In fall of 1976, when I took a
freshman algebra class at the local community college, my textbook had a chapter
on how to use a slide rule. My current mostused (on almost a daily basis) calculator is a
TI−85
programmable, graphing model that I've had since around 1992 (the year it was
introduced). It runs off of
four AAA batteries.
Calculators Get Smaller, Smarter and Cheaper
All the basics are shown on Panasonic's $70 Model 883 (left).
But similar Panasonic 840, now available, is smaller, costs only $50.
Here's how to pick the right one.
by Ivan Berger
Electronics Editor
Everything else may be going up in price, but calculators aren't  they're coming
down, dramatically. Handheld calculators, news when they first appeared for about
$400 each, have now come down to $16.95, with rumors flying of $10 calculators to
come.
That's probably rockbottom, though. The emphasis already has switched from how
inexpensively a calculator can be made to how well and conveniently it can be made
to work and still sell at a moderate price, and in the smallest package that will
still leave room to push its keys. Though wristwatchsize calculators (which have
been designed and could be built today) are probably too small to be really practical,
today's smallest can be very small indeed, yet still pack a lot of calculating power.
The Sinclair Scientific on our cover is a prime example. For just $69.95, it
does trigonometric and logarithmic calculations as well as the usual four calculator
functions (addition, subtraction, multiplication, and division) all in a package
just 4 1/2 by 2 by 11/16 inches (shown onethird larger on our cover). That's just
about everything you could get in a $30 slide rule, with a lot more accuracy (to
five significant figures) and a lot handier size. If you don't need a slide rule,
you can get a fourfunction, eightdigit Sinclair the same size, for just $40 
assembled or in kit form (see photo on age 72).
But just how much calculating power, and how many (and which) features do you
need  and do you need a calculator in the first place?
At today's prices, if you do enough arithmetic each month to grumble about or
enough to make occasional mistakes) you can probably both use and afford a calculator
 to help you check prices and unit costs when shopping, keep your checkbook straight,
or check your bills for accuracy. For the rockbottom minimum of calculation, something
like the $16.95 Novus will probably do fine, Its decimal point is present at two
places, for dollarandcents figuring, and its sixdigit display lets you add, subtract,
multiply or divide up to $9999.99  probably more than you usually keep in your
checking account.
But if you use it at all regularly, you may find yourself hankering for some
of the additional basic conveniences found on calculators like the Panasonic 883
at left. Having a decimal key, for instance, means you don't have to enter the zeros
for round numbers of dollars, and lets you multiply decimals (when figuring percentages,
for instance) without having to keep track in your head of where the decimal point
should wind up in the final result.
Cheapest calculatorat least as we go to press  is this $16.95
Novus 650 Mathbox, which lacks some desirable features, such as a decimalpoint
key.
Floating decimals, now found on most handheld calculators, show exactly as many
digits after the decimal point as there are significant figures to display  no
trailing, final zeros. Floating decimals are versatile, adapting themselves automatically
to each calculation for maximum accuracy; but since having no fixed decimalpoint
position can make fixeddecimal calculations like dollars and cents harder to read,
some calculators offer preset decimal settings as well. Common settings include
twoplace (for dollarandcent addition and subtraction) , threeplace (dollarandcent
multiplication and division, with the extra digit helping you round off correctly)
and five places (where you need high, but not overbearing, accuracy), A few calculators
will round off figures, raising the last digit by one if the next digit would have
been five or over, but most just cut off any figures that won't fit their displays.
In the latter case, most calculators underflow, displaying the highest, most
significant digits, and dropping off the less significant digits at the right of
the figure (usually with some indication that the answer shown is not complete and
of how many digits have been dropped before the decimal point). This indication
varies from machine to machine, though: Of the three typical calculators we tested,
one blinks, one displays apostrophes (easily overlooked, alas), and one has an overflow
key (a rather uncommon feature) that shows you any remaining digits when it's pushed.
A calculator's display must be big enough for you to see at a convenient working
distance, and must be visible from whatever viewing angle you'll be using: straight
up for handheld use, at about a 45° angle for use on a desk. The Sinclair Cambridge
(below) and Scientific, for instance, are very convenient for handheld use (you
can hold and operate them with the same hand) , but their narrow viewing angles
make them awkward on a desk. On the other hand, because the Casio's display is set
to one side of its keyboard rather than above, it becomes most convenient for desk
use and quite inconvenient when handheld, even though its display angle is wide
enough for any use.
Credit balance, a minus sign in front of negative results, is now almost universal
(some earlier calculators would show the result of four minus five as a string of
nines, rather than 1). But some minus signs are easier to read than others: Of
the calculators shown on these pages, for instance, the Panasonic shows it as a
red dot below and to the extreme left of the display, the Kings Point shows it as
a minus sign at the far left, and only the Sinclair and Casio show it clearly as
a minus sign immediately before the figure.
"T" setting on this Casio's onoff. switch controls memory. Most calculators
with memory use a separate switch
Memory ("M" on most machines, "T" on this one) stores intermediate totals, constants,
for later use
Percentage key eliminates decimal confusion when figuring percentages
Overflow key allows 16digit result on 8digit calculator, shows 8 digits at
a time; it's handy, but uncommon
Sinclair Cambridge comes assembled or in this threehour kit
(not for beginners) for $40. Size is identical to Sinclair Scientific (shown oversize
on cover).
The displays consume most of the power in the average calculator, far more than
do the transistors that perform the calculations. Some calculators are therefore
coming out with less powerhungry, liquidcrystal displays, whose digits darken
or turn silvery instead of lighting up. These are easier to read in bright light,
too, not "washing out" as selfilluminated displays do  but in dim light, they're
much harder to see, and some users have trouble seeing them from all but a few angles.
So if you're interested in liquid crystal display for longer battery life try it
under typical indoor illumination before buying it.
Batteries are very important, of course, in your selection of any portable device.
If you'll be using your calculator in one place all the time, or for several hours
each place you use it, you might prefer an a.c. operated, desktop model that must
be plugged in to operate, but offers the advantage of a larger display and more
comfortablyspaced keys. If you frequently use your calculator in one place, but
do need to use it portably from time to time, a handheld model with rechargeable
battery is probably your best bet. If you travel a lot, running the risk of leaving
your recharger home, you're safest with a model whose batteries can be replaced
when dead, especially if they're easytofind types such as 9volt "transistor"
batteries, or AA "penlight" cells (smaller AAA batteries, or hearingaidtype mercury
cells are harder to find). Even the disposablebattery types, though, often have
sockets for optional power supplies, so you can conserve battery life by running
them from your a.c. house current or off your car's battery whenever possible.
The keyboard is important, too. The keys themselves should fit your fingers,
feel good, and give you some sort of tactile indication that you've pressed the
key in far enough to complete entry. We're partial to keyboards that "click" when
pressed, but we've heard that some may click without registering if you press the
side rather than the top of the key; check all the keys for that before you buy.
Check, too, that no keys stick, and that the calculator won't register a number
twice if you accidentally tap the key so fast its contacts bounce. Keys should also
be big enough to hit easily, and far enough apart to minimize the chance you'll
hit the wrong one.
Scientific calculators are specialized tools, but their prices are coming down
into the consumer brackets.
Radian/degree conversion switch. If you don't know what radians are, you don't
need it
Scientific notation shows figures as mantissa" multiplied by powers of 10 in
exponent
Trigonometric Function Keys
Pi keys saves entering 3 to 10 digits
Brackets and parentheses let you complete one calculation within another, partiallyfinished
one
A look at the keyboard will also tell you whether it uses algebraic or arithmetic
entry. Algebraic keyboards, with separate keys for +, , and =, let you key in additions
and subtractions exactly as you'd write them down. Arithmetic keyboards, recognizable
by their += and = keys, require a slightly different key sequence: you push +=
after all positive numbers, = after all negative numbers or numbers to be subtracted
(multiplication and division are the same for both key systems). Though the algebraic
system is more natural, most people, we find, can pick up the arithmetic system
in no time flat. The only problem occurs when you're switching between calculators;
so if you're buying more than one for your family or business, make sure they all
use the same entry system.
A "clear" key is a must, and a separate "clear entry" key is a major convenience
if you ever do long calculations. The clear key erases the whole calculation and
resets the machine to zero  handy, if you find you've set the calculation up wrong,
or made an error a few steps back. Clear entry keys just erase the last entry you
made, so you can correct that without disturbing all the correct steps you've made
before. Some calculators have a single CE/C key, whose first stroke clears the last
entry, and whose second clears the entire example; this is probably almost (but
not quite) as convenient.
Extra features handy for most home calculations are shown in
the Casio $40 Mini Memory (right), found in many other common calculators as well.
For common percentage calculations, such as discount, tips and taxes, many calculators
have percentage keys which automatically adjust the decimal point as needed.
Memory and constant memory are useful extras found on many middlepriced machines.
The constant memory lets you repeatedly multiply or divide by the same number without
having to reenter it each time (and often lets you add or subtract it repeatedly
as well). A K switch or button is a common sign of a constant memory, though many
calculators without the switch still have a constant memory built in (for instance,
the Sinclair, the Panasonic and the Casio did). On such machines, once you've multiplied
a number by the desired constant, all you have to do to multiply another number
by the constant is to key in that number and the equals sign.
You can also square a number on a constantmemory machine by keying in the number,
X and =.
The accumulative memory, shown on the Casio on page 72, is a bit less common.
It automatically adds together all totals of a series of intermediate calculations:
Every time you hit the "equals" key, that result is added to whatever is in the
memory. A typical application would be making invoices: Multiply a dozen apples
at 12 cents apiece ($1.44) and 16 clams at $1.25 per dozen ($1.666 ... ) and all
you have to do is press the recall button (T on the Casio ) to get the total of
the invoice; $3.1066 ... or $3.11.
On some machines, the Casio included, if you shut off the accumulator, you can
still recall and use its contents though further totals won't be added to the memory.
To subtract a total from the accumulator, there's usually a red = key.
This Kings Point SC40 is $150; Sinclair Scientific on cover
is less versatile, but is only $69.95.
Calculator you can program to perform sequences of operations
automatically is HewlettPackard's $795 HP65; 950 premade programs are also available.
Business calculators are as complex as scientific types, but
are preprogrammed for typical business calculations. HewlettPackard's new HP70
costs $275.
A singlekey memory has a single M key that performs two functions: Press it
while there's a number on the display, and the memory will clear itself, then memorize
that number; press it after a function key (+ or X, for instance), and it will recall
the memorized number to the display.
Fullcontrol memories have keys labeled M+, M, MR and sometimes MC. Pressing
the first of those keys adds the number on the display to the memory; pressing the
second subtracts the displayed number from the memorized total; pressing MR brings
the total from the memory to the display; and MC clears the memory. Fullcontrol
memories can store constants, intermediate results, accumulative totals, or any
other number. Some desktop calculators may have more than one such memory.
Itemcount memories are rarer, and are mostly used for things like invoicing.
In the example given for accumulative memory, an itemcount would have added up
the dozen apples and the 16 clams to come up with 28 items.
Printing calculators are rare in home use, since they're slowerworking than
display types, bigger (with the exception of the pocketsized Canon), and cost more
(about $150 up). But for accountants or others who need a printed record of their
figuring, printers are invaluable.
Not all calculators, of course, are built for the home. More and more, in fact,
are built for scientific or business uses. Scientific types, often called "electronic
slide rules," offer several features home calculators don't have  or need. Virtually
all scientific models have square root keys, but that key alone doesn't really make
them "slide rules," though some ads might make you think so. For scientific use,
a calculator usually needs keys for such trigonometric functions as sine and tangent,
and for calculations using both common (base10) and natural (baseE) logarithms.
Since pi occurs frequently in many formulas, a key that enters it with one stroke
can save your having to punch in and remember up to 10 digits (3.1415926654) each
time that you need it.
Scientific notation greatly expands a calculator's range. By dividing a number
into significant digits and powers of 10, you can shorten a figure like one billion
from 1,000,000,000 down to 1x109, giving a calculator with two exponent places (for
showing powers of 10) a capacity to display numbers that would otherwise require
100 digits or more to display if written out in full. Some calculators give you
the option of entering numbers in conventional or scientific notation; others (usually
without a decimal point key) may allow only scientific, which makes them much less
useful for common household figuring.
Radians are used instead of degrees to specify angles in many scientific formulas,
so scientific calculators often have switches to set their trigonometric functions
to work with either unit (as on the Kings Point shown on page 74), or to convert
from degrees to radians or vice versa.
Scientific calculators with algebraic entry often have parenthesis and bracket
keys, to allow one calculation to be performed within another, such as [ (3x2) +
(3+4) ] +1 (7x5)  (5x4) ] = 0.45. Others use Polish notation, or reverse Polish
notation (signified by the presence of a key labeled ENTER, but no = key), which
read equations from left to right without the need for parentheses or brackets.
Algebraic entry is easier to learn (you're already using it when you use pencil
and paper), but involves more key strokes.
Some scientific calculators have many more functions than we've described. Many,
in fact, have more functions than they have keys; a shift key (the Sinclair on the
the cover has two of them) changes their keys' functions.
Scientists aren't the only ones with complex calculation to perform. Special
calculators are now available for businessmen, statisticians and others, with more
likely to come, Simpler specialized calculators are available (including a $75 MITS
kit) with metrictoEnglish measurement conversions as well as the usual four arithmetic
functions. At the other end of the scale, programmable calculators can take recorded
instructions outlining long and complex series of operations, including specialized
instructions for anything from pinetwork impedance matching to reconciling a checkbook
 to name just two programs in the basic pack supplied with HewlettPackard's HP65.
Even these complex functions can be performed, though less quickly and conveniently,
using only a standard, fourfunction calculator, appropriate formulas, and perhaps
a book of logarithmic or trigonometric tables. That is, after all, how scientists
did things for years  but faster and more accurately, with the calculator doing
the actual computations.
For specifics on how to use simple calculators for complex figuring, you can
get a thin but meaty pamphlet for $2 from Mallman Electronics, 836 South 113th St.,
West Allis, Wis. 53214 and a much more detailed book, Fingertip Math, from Texas
Instruments.
Posted November 22, 2019
