Formulas That Update

Here's the moment spreadsheets earn their keep. Put =A1+A2 in B1, then go change A1. The instant you press Enter, B1 shows the new sum. No button to press, no formula to retype, recalculation is automatic.

Why? Because the cell never stored the answer. It stored the recipe, "add A1 and A2", and Excel re-runs the recipe whenever an ingredient changes. A formula depends on the cells it references, and Excel quietly tracks every one of those dependencies.

That's the crucial difference between typing a value and writing a formula. If A1 is 5 and A2 is 3, typing 8 into B1 looks identical to typing =A1+A2. But change A1 to 10 and the typed 8 sits there, wrong forever, while the formula flips to 13 on its own.

This is how professionals build spreadsheets: enter each piece of raw data once, and compute everything else with formulas. Then updating a whole report is just editing a few cells and letting the updates ripple through.