An electronic spreadsheet is a program that presents a two-dimensional grid of cells, each addressed by a column letter and a row number, into which a user can enter numbers, text labels, or formulas. The defining feature is automatic recalculation: when a cell’s value changes, every formula that refers to that cell, directly or through a chain of other cells, updates immediately. This turns a static table of figures into a live model that responds to changes in its inputs.
The concept was introduced to personal computers by VisiCalc in 1979. The original VisiCalc manual, archived at bitsavers, teaches the user to think of the screen as an “electronic worksheet” that replaces the paper ledger sheet an accountant would use, with the crucial difference that the machine does the arithmetic and keeps the totals consistent automatically. Dan Bricklin, who designed VisiCalc, describes on his own site how the goal was to capture the back-of-the-envelope financial modeling that business people did by hand and make it instant and error-free.
The power of the model comes from the formula and the cell reference. Because a formula can name other cells rather than fixed numbers, a spreadsheet captures the structure of a calculation, not just its result. A user can change an assumption in one place and watch the consequences ripple through projections, budgets, and totals. This made the spreadsheet the first widely used tool for what-if analysis, and it is why the spreadsheet became the original killer application of the personal computer.
Over time the core grid acquired more capability. Lotus 1-2-3, released in 1983, added built-in functions, business graphics, and simple database operations to the same recalculating grid, and tuned it for the IBM PC. Microsoft Excel later brought the model to graphical interfaces with the mouse, charts, and macros. Through all of these the underlying idea has stayed remarkably stable: a grid of cells, formulas that reference other cells, and automatic recalculation.
The spreadsheet remains one of the most widely used kinds of software in the world, found in finance, science, operations, and everyday personal accounting. Its conceptual lineage runs in an unbroken line from VisiCalc, which is why the spreadsheet is studied as both a technical model and a turning point in who could use a computer and for what.