A software calculator is a calculator that has been implemented as a computer program, rather than as a physical hardware device. They are among the simpler interactive software tools, and, as such, they provide operations for the user to select one at a time. They can be used to perform any process that consists of a sequence of steps each of which applies one of these operations, and have no purpose other than these processes, because the operations are the sole, or at least the primary, features of the calculator, rather than being secondary features that support other functionality that is not normally known simply as calculation. As a calculator, rather than a computer, they usually have a small set of relatively simple operations, perform short processes that are not compute intensive and do not accept large amounts of input data or produce many results. Platforms Software calculators are available for many different platforms, and they can be: A program for, or included with an operating system. A program implemented as server or client-side scripting (such as JavaScript) within a web page. Embedded in a calculator watch. Also complex software may have calculator-like dialogs, sometimes with the full calculator functionality, to enter data into the system. History Early years Computers as we know them today first emerged in the 1940s and 1950s. The software that they ran was naturally used to perform calculations, but it was specially designed for a substantial application that was not limited to simple calculations. For example, the LEO computer was designed to run business application software such as payroll. Software specifically to perform calculations as its main purpose was first written in the 1960s, and the first software package for general calculations to obtain widespread use was released in 1978. This was VisiCalc and it was called an interactive visible calculator, but it was actually a spreadsheet, and these are now not normally known simply as calculators. The Unix version released in 1979, V7 Unix, contained a command-line accessible calculator. Simulation of hardware calculators Calculators have been used since ancient times and until the advent of software calculators they were physical, hardware machines. The most recent hardware calculators are electronic hand-held devices with buttons for digits and operations, and a small window for inputs and results. The first software calculators imitated these hardware calculators by implementing the same functionality with mouse-operated, rather than finger-operated, buttons.