The Sharp QT-8D (also known as the "Micro Compet") has the distinction of being recognized as the first electronic calculator marketed to be implemented using large-scale integrated (LSI) circuits. The development of this calculator was a breakthrough, paving the way for LSI's to dramatically increase the capability and decrease the size, and more importantly, the cost, of electronic calculators.

Prior to the development of Large Scale Integrated circuits for electronic calculators (one of the first consumer applications of LSI devices), electronic calculators relied on many small and medium-scale integrated circuits, along with fairly substantial quantities of individual discrete components such as transistors, diodes, resistors, and capacitors. For an example of Sharp's Pre-LSI calculator technology utilitizing small and medium-scale integrated circuits, see the exhibit on the Sharp Compet 16.

Small Scale (SSI) IC's contain the equivalent of 20 or so logic gates, making up a flip flop or two, or a selection of a few logic gates. Medium Scale (MSI) integrated circuits contain more logic, around 100 or so gates. In an MSI device, functions such as an 8-bit shift register, 4-bit data selector, or binary full-adder circuit could fit on a single chip. Later medium-scale MOS (Metal Oxide Semiconductor) devices could place an entire 64-bit shift register in a single chip. These devices paved the way for the development of Large Scale integrated circuit technology. LSI devices made it possible to cram hundreds, and later, thousands of logic gates onto a single chip of semiconductor material. This made it possible for an entire subsystem of an electronic calculator (for example, the arithmetic unit) to be integrated down to a single chip. LSI devices, while initially expensive to develop, became easier and easier to manufacture as the processes became better understood and more refined. Use of LSI integrated circuits in calculators allowed calculator manufacturers with access to LSI technology (or alliances with those that had the technology) to substantially reduce their costs to make a calculator, which in turn resulted in lower cost for the consumer.

The story of the development of the QT-8D, as well as the emerging power of Sharp as a major force in the electronics industry, is a rather long journey, however, it follows the pattern of so many other successful high-technology businesses. The force behind Sharp's dominance in the electronic calculator marketplace was driven by a gifted individual, someone with the genius, vision, discipline, and persistence to lead the company into a new realm. For Sharp, that man was Tadashi Sasaki.

Tadashi Sasaki was born in 1915. The exact place of his birth isn't known for sure. He may have been born in Taiwan, or in Japan. In any case, his homeland is considered to be Japan. As Sasaki progressed through his schooling, with the focus of his studies being Japanese literature, one of his teachers recommended to him that he should consider directing his energy into the sciences. Sasaki took this to heart, and began studying the sciences with great diligence.

The QT-8D uses an unusual keyboard layout. Note the combined "X÷" key. Sharp used a novel means to save a key on the keyboard (thus saving the cost, as well as decreasting the real-estate needed for the keyboard) by making the "X÷" key serve both functions. The determination as to which function the user wishes is made by the user selecting either the "+=" key to generate the result for multiplication, and the "-=" key to cause division to occur. For example, to multiply, the user would enter the first number, press the "X÷" key, then enter the multiplier, then press the "+=" key for the answer. To divide, the user would enter the dividend, press the "X÷" key, enter the divisor, and press the "-=" key to calculate the answer.

The keyboard uses magnetic reed switches. This is one of the most expensive means for providing a keyboard, but is extremely reliable. The magnet/reed switch design results in a keyboard that still works perfectly over 30 years later, with no 'double entry' or incosistent operation problems. The keyboard assembly connects to the backplane via a neatly bundled wire harness. The keycaps have moulded-in nomenclature, and are made of high-quality plastic. The keyboard has a great feel to it. Sharp's calculators tended to always have very nice keyboards, and the QT-8D is no exception.

The rear part of the calculator contains the power supply electronics. The machine uses a traditional transformer/rectifier setup, with transistor regulation. The power supply, like all of the other parts of the machine, is of high quality, using large filter capacitors and generous heatsinking. A special three-prong cord plugs into a socket on the rear panel of the machine.

The QT-8D is a relatively fast calculator, even though it is using very early LSI technology. The "all-nines" divided by one benchmark takes about 0.2 second to perform. Addition and subtraction complete with virtually no delay. The machine properly handles negative numbers, lighting the "-" indication in the special tube at the right end of the display. The machine also accurately detects overflow, lighting the 'dot' indicator at the right end of the display. The QT-8D does not detect divide by zero properly, and goes into a strange state which requires the machine to be cleared with the "C" key before it will return to normal operation.

Like many other Sharp calculators, the QT-8D was offered to Sharp's OEM customers for repackaging and sale by other manufacturers. Included among these were long-time Sharp OEM customer Facit, with the Facit 1115, as well as Addo-X, with the model 9354. The OEM versions of the QT-8D were identical inside, with the main differences being cabinetry styling, color scheme, and badging.

The Sharp QT-8D also appears to have a place in electronic calculator history within the former Soviet Union. A Soviet copy of the QT-8D, called the Electronika 24-71, was developed by reverse-engineering the QT-8D. Leadership of the Soviet Union had become very concerned about the state of electronics in the 1960's. Many military systems still utilized vacuum tubes, and had only recently began utilizing solid-state (transistor) devices. The Soviet Union only had small-scale microelectronic devices in laboratory facilities, which were generally copies of devices developed in Europe and the United States. Large Scale Integration, which had started to make potential inroads into consumer electronics as early as 1965 in the US, and by late 1967 in Japan, was only a gleam in the eye of Soviet technical leadership. An aggressive program was put into place in 1969, with a promise made to then Soviet President Leonid Breshnev that he would have a Soviet-made Large-Scale Integration-based calculator on his desktop at the opening of the 24th Communist Party Congress in 1971. (Note the Soviet machine's model number of 24-71 was based on the 24th Congress, and 1971). The Soviet scientists and engineers were successful in duplicating the LSI chips themselves, but had difficulty with packaging them. In order to make the presentation to President Breshnev as promised, a Sharp QT-8D was acquired, disassembled, and its electronic guts repackaged into a Soviet-made cabinet, with a Soviet-made display based on the Japanese-design Itron vacuum-fluorescent display tubes used in the QT-8D (with a comma instead of a decimal point), and a Soviet-made keyboard assembly with Cyrillic keycaps. Soviet President Breshnev had no idea that his prized posession was just a repackaged Japanese calculator. It took until 1973 before the chip packaging issues had been solved, and the calculator went into production and sales, with a selling price of 100 Rubles (about US$85 back them).