Calculators Get Smaller, Smarter and Cheaper
December 1974 Popular Mechanics

December 1974 Popular Mechanics
December 1974 Popular Mechanics - RF Cafe[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 American-made 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 most-used (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

Calculators Get Smaller, Smarter and Cheaper, December 1974 Popular Mechanics - RF Cafe

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. Hand-held 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 rock-bottom, 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 wrist-watch-size 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 one-third 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 four-function, eight-digit 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 rock-bottom minimum of calculation, something like the $16.95 Novus will probably do fine, Its decimal point is present at two places, for dollar-and-cents figuring, and its six-digit 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.

$16.95 Novus 650 Mathbox calculator - RF Cafe

Cheapest calculator-at least as we go to press - is this $16.95 Novus 650 Mathbox, which lacks some desirable features, such as a decimal-point key.

Floating decimals, now found on most hand-held 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 decimal-point position can make fixed-decimal calculations like dollars and cents harder to read, some calculators offer preset decimal settings as well. Common settings include two-place (for dollar-and-cent addition and subtraction) , three-place (dollar-and-cent multiplication and division, with the extra digit helping you round off correctly) and five places (where you need high, but not over-bearing, 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 under-flow, 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 hand-held use, at about a 45° angle for use on a desk. The Sinclair Cambridge (below) and Scientific, for instance, are very convenient for hand-held 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 hand-held, 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 on-off. 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 16-digit result on 8-digit calculator, shows 8 digits at a time; it's handy, but uncommon

Sinclair Cambridge comes assembled or in this three-hour kit - RF Cafe

Sinclair Cambridge comes assembled or in this three-hour 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 power-hungry, liquid-crystal displays, whose digits darken or turn silvery instead of lighting up. These are easier to read in bright light, too, not "washing out" as self-illuminated 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 comfortably-spaced keys. If you frequently use your calculator in one place, but do need to use it portably from time to time, a hand-held model with rechargeable battery is probably your best bet. If you travel a lot, running the risk of leaving your re-charger home, you're safest with a model whose batteries can be replaced when dead, especially if they're easy-to-find types such as 9-volt "transistor" batteries, or AA "penlight" cells (smaller AAA batteries, or hearing-aid-type mercury cells are harder to find). Even the disposable-battery 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, partially-finished 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.

Casio $40 Mini Memory - RF Cafe

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 middle-priced machines. The constant memory lets you repeatedly multiply or divide by the same number without having to re-enter 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 constant-memory 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.

Kings Point SC-40 is $150 calculator - RF Cafe

This Kings Point SC-40 is $150; Sinclair Scientific on cover is less versatile, but is only $69.95.

Hewlett-Packard's $795 HP-65 - RF Cafe

Calculator you can program to perform sequences of operations automatically is Hewlett-Packard's $795 HP-65; 950 premade programs are also available.

Hewlett-Packard's new HP-70 costs $275 - RF Cafe

Business calculators are as complex as scientific types, but are preprogrammed for typical business calculations. Hewlett-Packard's new HP-70 costs $275.

A single-key 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.

Full-control 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. Full-control memories can store constants, intermediate results, accumulative totals, or any other number. Some desktop calculators may have more than one such memory.

Item-count memories are rarer, and are mostly used for things like invoicing. In the example given for accumulative memory, an item-count 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 slower-working than display types, bigger (with the exception of the pocket-sized 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 (base-10) and natural (base-E) 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 metric-to-English 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 pi-network impedance matching to reconciling a check-book - to name just two programs in the basic pack supplied with Hewlett-Packard's HP-65.

Even these complex functions can be performed, though less quickly and conveniently, using only a standard, four-function 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