The GPA, also marked "PC-1", was marketed by consumer giant Gillette in the mid 1970's. This was the only model marketed by Gillette, and was manufactured by Gillette by Sinclair Radionics of Great Britain. The calculator has an eight-digit LED display and is powered by a single 9-volt battery. The machine has a jack for an AC power adapter but it did not come with one and there is no mention of using an adapter on the box or in the instruction booklet. It has a dark gray case, with white buttons for the numeric entry keys and orange keys for the functions and decimal point. The function keys are: K, C, CE, divide, X, -, +, and =. It uses standard algebraic logic.
This calculator has several interesting characteristics. Unlike most pocket calculators, the numeric display is left-justified, except during entry of a number. During numeric entry, the display fills with "0"s and the digits replace the "0"s from right to left as they are keyed in. Once a function key is pressed the extra "0"s disappear and the number is then left-justified.
The calculator appears to have a 9-digit LED display module, but only eight of them are used. In the case of a negative number, the "-" sign appears in the leftmost of the used digits (the unused digit of the display module is at the far left), an only up to seven significant numerical digits can be displayed.
The CE, Clear Entry key, is used if a mistake is made keying in a number, but if you use CE you also have to press the function key from the operation in addition to the re-entered number, instead of just having the numeric entry cancelled.
The K key is used for entering a constant. The instruction booklet has the following example:
store 3 as a constant for the problem 6 + 3 + 3 = 12 Enter 3 displays 00000003 Press = displays 3. Press K displays 3. Enter 6 displays 00000006 Press + displays 9. Press + displays 12. Note:If function is used without preceeding number the constant will be added to, subtracted from multiplied by, or divided into the number on the display. (6 + 3 + 3) X 3 Press X displays 36. To retain and use previously stored number as constant do not press C or CE between calculations, just enter number.
An unusual feature of the calculator that is beyond the capabilities of most four-function calculators is its ability to handle calculations beyond the range of 8 digits. The instruction booklet claims that the calculator will function with numbers ranging from 10E-20 to 10E+79, stating that answers smaller than .00000001 will be displayed as 0; however, repeated multiplication by 10 will eventually cause the eight most significant digits to be displayed. Answers larger than 99999999 will have their eight most significant digits displayed without a decimal point. Repeated division by 10 will cause the decimal point to appear in the display. The booklet advises that you must manually keep track of how many times you divided or multiplied by 10 to know where the decimal point belongs. This feature was called "Data Bank Storage".
The calculator clearly was aimed at the mass consumer market. The machine was delivered in an 8"x8" silver-tone box with a picture of the machine, a picture of a happy couple balancing their checkbook with a GPA, an a list of features including "8 digit display (not 6)", "Data Bank Storage (retains very large numbers)", and "Positive click-entry keys". The box also has "(Gillette Personal Accountant)" marked in several places, indicating what GPA stands for. Inside the box, side by side, were the calculator and a small 34-page booklet titled DOLLARS AHEAD some good ways to save with your Gillette GPA Pocket Electronic Calculator. The first 20 pages are devoted to descriptions of things the calculator can be used for, like home budgeting, checking account management, etc. The instructions on how to use the calculator are in the final 14 pages. The booklet that came with my GPA has the date printed listed as 8/74. Given the timing, that explains why one of the features listed on the side of the box was "Now you can do something to fight inflation." Remember the WIN buttons???
The rear side of the calculator is labelled as follows:
Gillette GPA tm Pocket Electronic Calculator Model PC-1 Distributed by: The Gillette Company Appliance Division Boston, Mass. 02119 Made in England