The most widely used reactive program

Both examples in the previous section will feel familiar to some readers. If we call the input text fields cells and the result label's handler formula, we now have the nomenclature that's used in modern spreadsheet applications such as Microsoft Excel.

The term Reactive Programming has only been in use in recent years, but the idea of a reactive application isn't new. The first electronic spreadsheet dates back to 1969, when Rene Pardo and Remy Landau, then recent graduates from Harvard University, created LANguage for Programming Arrays at Random (LANPAR)[1]. 

It was invented to solve a problem that Bell Canada and AT&T had at the time: their budgeting forms had 2,000 cells that, when modified, forced a software rewrite, taking anywhere from six months to two years to complete.

To this day, electronic spreadsheets remain a powerful and useful tool for professionals in various fields.