Since the 1960s, modern technology has entirely transformed our means of manipulating numbers. Today’s electronic calculators are a remarkable feat of miniaturization and performance. And they are available at outstandingly low cost.
In operation, calculators rely on the use of a very simple mathematical process. They can only add and subtract using a simple code of ones and zeros, a system known as binary notation. There are ways of carrying out most mathematical computations through long routines of adding, shifting, and testing, all of which are impracticably tedious.
Using a calculator, which can typically perform several million such operations per second, the results of calculations that would take several hours for a human brain to perform appear virtually instantaneously.
Semiconductors
It was in the 1960s, when new semiconductor technologies first allowed hundreds of thousands of transistors to be squeezed into small blocks of silicon—a process known as large-scale integration—that the task of building a small electronic calculating machine became feasible. The large-scale integrated circuit, abbreviated to LSI, is a form of silicon chip. Current types contain tens of thousands of transistors that are designed to perform various functions, from mathematical calculations to memory storage, using binary logic.
Early models
The first electronic calculators were limited by the number of individual transistors that could be placed on one silicon chip, the amount of electrical power required to drive each function, and the cost of manufacturing the chips. With advances in manufacturing techniques, basic calculator chips have moved from being about the most complex devices produced to some of the simplest; consequently, the costs have fallen rapidly. In a modern basic calculator, the silicon chip represents only a small percentage of the final product cost—the display, keyboard, and case form by far the largest cost elements. Thus it is possible to introduce enhanced calculators with additional functions produced by larger, more complex chips without greatly increasing the overall product cost. Innovations such as biorhythm calculators, music generators, and gameplaying facilities improve sales, are simple to implement, and are therefore very popular with marketing departments.
The earliest and commonest container for integrated circuits was the dual-in-line (DIL) package. For a typical calculator chip of 1/16 sq. in. (less than 0.5 cm2), this is a relatively enormous package of about 1 sq. in. (7 cm2). Newer packages such as flat packs and leadless chip carriers require far less space and allow calculators to be built into very confined spaces such as imitation credit cards, rulers, and watches.
Electronic calculators are organized into various functional blocks. The input unit converts decimal keyboard entries into binary code and may hold the information until it can be fed into the central processing unit (CPU), which carries out all calculations. Instructional entries, such as a "divide" command, are routed through to a read-only memory, which then instructs the CPU how to process the data fed in from the keyboard. Finally, an output unit holds the answer from the CPU and turns it into a form that drives a visual display, which can then be read.
