INTRO : Entering Formulas, Copying, and Pasting

Figure 1. Data in the active cell and the Formula Bar

Select cell A1. Type the number 3 and press the ENTER key. If the cursor is not in cell A2, select the cell. Now type the number 5 and press the ENTER key. Select cell A3 if it is not already selected, type =SUM(A1:A2), press the ENTER key, and the sum, 8, appears in cell A3, as shown in Figure 4.
Alternately, select cell A3 and click on the summation icon in the Tool Bar ( ). This enters the formula automatically into cell A3; there is no need to type it. Pressing the ENTER key or clicking the checklist (V) icon on the Tool Bar gives the answer. The formulas also can be seen in the Formula Bar by clicking on cell A3 to make it the active cell.
To copy the contents of cells, highlight them, click on the right mouse button, and select copy from the menu (or click on Edit on the Menu Bar and select Copy). Then click on the upper left corner of the area to which you want to copy the cells. For example, highlight cells A1:A3 and copy them as just explained. Then click on cell C1, depress the right mouse button, and select paste (or click on Edit on the Menu Bar and select Paste). Figure 2 presents the results.
The contents of cells A1:A3 appear in cells C1:C3. Now click on cell C3 and observe the formula: =SUM(C1:C2). Notice that this formula is different from the one in cell A3, =SUM(A1:A2).

Figure 2. Relative references

The cell references in a formula like in cell A3 are called relative references because when the formula is copied, Excel remembers the cell references relative to the cell in which the formula is contained. As an illustration, the formula in cell A3 sums the numbers in the two cells directly above it, A1:A2. The formula in cell C3 does the same. It sums the numbers in the two cells directly above it, C1:C2 in this case. To get a better idea about how a relative reference works, delete the contents of cells C1:C3, highlight just cell A3, and copy its contents to cell C3. A zero results because the formula is summing the two blank cells above C3 as shown on the left-hand side of Figure 3.
Figure 3. Relative verses absolute references

If the formula in cell C3 sums the two numbers in cells A1:A2, then an absolute reference must be used. A cell reference is called an absolute cell reference if dollar signs are used ($) before the letter and number. For example, in cell A3 type in the formula =SUM($A$1:$A$2) as shown on the right-hand side of Figure 3. In this formula the references to cells $A$1:$A$2 are called absolute references. This means that when this formula is copied to any other cell the results will always give the sum of the cells A1:A2. Consequently, with 3 in cell A1 and 5 in A2, copying A3 to C3 gives 8 with the absolute references in the formula as compared with 0 with the relative references. This is shown on the right-hand side of Figure 3.