Copying formulas and how references behave

When you copy a formula to a neighboring cell, Excel automatically shifts the cell addresses — this is called a relative reference. For example, if C2 contains =A2+B2 and you copy the formula to C3, it becomes =A3+B3. That's handy for calculating totals for each row. But sometimes you need to lock a reference so it doesn't shift. To do that, you add dollar signs: $A$1 is an absolute reference — it changes neither its row nor its column. $A1 locks only column A; A$1 locks only row 1. These are mixed references. A classic scenario: a sales table with the grand total in cell B8. To calculate each product's share, write the formula =B2/$B$8 in C2 and copy it down. The $ signs in $B$8 make sure the divisor doesn't shift. Without them, the formula in C3 would become =B3/B9 — a wrong result. An easy way to add $: put the cursor on the reference in the formula bar and press the F4 key. Excel cycles through A1 → $A$1 → A$1 → $A1 → A1.