A Function is a predefined formula whose definition is already explained to Excel.  We have to just select the name of the function and supply arguments or values to it. Each argument is separated by a comma and total list of arguments is enclosed within parentheses.  Each function has a syntax that specifies the number and order of its arguments.  The arguments of functions can be numbers, cell addresses or even range of cells.  The maximum number of arguments of any function is 255 in Excel 2007.

Example of Fuction:

=SUM(a1,c4)

=SUM(3,5)

=SUM(C4:C9)

Entering Function:

1. Formulas TabàFunctions Library Group
2. Select a function Name from the Function Groups

(or)

1. Click on Insert Function Button beside formula bar
2. Insert Function Dialog Appears
3. Enter the description of function you want in “Search for a function” Text box
4. Or Select a category of function from Category drop down list
5. Then select your required function from the list box below

(or)

Directly type the function along with its arguments followed by equal to sign

SOME OF EXCEL FUNCTIONS THAT ARE COMMONLY USED:

SUM: returns the sum of values in the specified range of cells. 

Syntax: =SUM(list of arguments)

using Autosum:

1. select range of cells including a blank cell in which total to be appear.
2. click on Autosum button on standard toolbar (or) press alt+=

AVERAGE: returns the average of values in the specified range of cells.

Syntax: =AVERAGE(argument list)

MAX: returns the maximum value in the specified range of cells.  It only considers numeric data.

Syntax: =MAX(arg list)

MIN: returns the minimum value in the specified range of cells.  It only considers numeric data.

COUNT: returns the number of cells containing numeric data.

COUNTA: returns the number of cells containing data (both numeric and text).