How does Excel automatically sum?

how does Excel automatically sum

1, first say automatic summation bar, note that I use Excel is 2007 version, table diagram, relatively simple, I want to calculate the number of 1 and 2 and

2, first select the first sum cell C2, and then select the menu [insert], point [formula] tab, as shown

3, point [Auto sum],[sum]

4, after the point [sum], the C2 cell becomes as shown, more than one sum formula, sum is the formula for summation, which means that the current row is a2:b2 from A2 cell to B2 cell, and no matter how many other cells there are between the two cells, the cell from the left of the colon is added to the right cell. This is a whole line of cumulative

5, press the keyboard on the right keypad to confirm the key (small enter), the results are automatically out as shown

6, then below look at the C2 below C3,c4 and so how to let them automatically come out results, mouse click to select C2 cell, C2 border into the soiled box, black box in the lower right corner of several small four squares, the mouse moved to the square block where the mouse into a solid cross as shown

7, the mouse into a solid cross, hold down the mouse pull down to the need to fill the data table as shown, the results automatically came out

8, when the number 2 input data, click the corresponding peer to the right results automatically calculated results as shown

9, the above said a whole line of data automatically added, a whole column of data automatically add operation, select the number 1 column to calculate and the cell A11, select [Auto sum],[sum] on it, if the number 2 that column also need to sum, click the above method to select A11 to the right to pull down the mouse to the B11 can be