Excel's Formula - sisman

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Part I: Basic Information
Values or text strings: Examples include 7.5 (a value) and “Year-End Results” (a string,
enclosed in quotes).
Worksheet functions and their arguments: These include functions such as SUM or
AVERAGE and their arguments. Function arguments appear in parentheses, and provide
input for the function’s calculations.
Parentheses: These control the order in which expressions within a formula are
evaluated.
Entering a formula
When you type an equal sign into an empty cell, Excel assumes that you are entering a formula
because a formula always begins with an equal sign. Excel’s accommodating nature also permits
you to begin your formula with a minus sign or a plus sign. However, Excel always inserts the
leading equal sign after you enter the formula.
As a concession to former Lotus 1-2-3 users, Excel also allows you to use an “at” symbol (@) to
begin a formula that starts with a function. For example, Excel accepts either of the following
formulas:
=SUM(A1:A200)
@SUM(A1:A200)
However, after you enter the second formula, Excel replaces the @ symbol with an equal sign.
You can enter a formula into a cell in one of two ways: Enter it manually, or enter it by pointing
to cells that are used in the formula. I discuss each of these methods in the following sections.
Entering a Formula Manually
Entering a formula manually involves, well, entering a formula manually. You simply activate a
cell and type an equal sign (=) followed by the formula. As you type, the characters appear in the
cell as well as in the Formula bar. You can, of course, use all the normal editing keys when typing
a formula. After you insert the formula, press Enter.
When you type an array formula, you must press Ctrl+Shift+Enter rather than just Enter.
An array formula is a special type of formula, which I discuss in Part IV.
After you press Enter, the cell displays the result of the formula. The formula itself appears in the
Formula bar when the cell is activated.