Spreadsheets and
Microsoft Excel
Introduction
A spreadsheet (called a worksheet in Excel)
is a two-dimensional array of cells
containing data to be computed and
analyzed.
 Each cell may contain text, often used as
row or column headings, numerical values,
or formulas, which are used to compute
other numerical values.
 Cells may contain other types of data too.


Here is a particular example, including
additional formatting features, like text that
spans multiple cells and color:
Formula Bar
The real power of spreadsheets comes from
the use of formulas, which tell Excel how
the values displayed in certain cells are to
be computed from the values displayed in
other cells.
 To use formulas, we need to first understand
how to refer to the values in individual
cells, or cell references.

For example, the cell containing Adams’s
overall score is referred to as cell E6
because it’s in column E and row 6.
 If we make E6 the active cell by moving the
cursor there and clicking, Excel displays
this:

In particular, what we see in the formula bar
is
=$B$4*B6+$C$4*C6+$D$4*D6
 This means that the value 88.0 displayed in
cell E6 is actually computed from the values
displayed in other cells.
 To understand this particular formula, first
ignore the $ signs. They’re important to
understand eventually, but for now, pretend
they’re not there.


What this formula says is, to determine the
value to display in cell E6:
–
–
–
–
Multiply the value in cell B4 times the value in
cell B6.
Multiply the value in cell C4 times the value in
cell C6.
Multiply the value in cell D4 times the value in
cell D6.
Then add these three values together.

That is, the value in cell E6 is computed as:
(0.25)*(100)+(0.25)*(90)+(0.50)*(81)
= 88.0


The beauty of using a formula in a spreadsheet is
that if any cells’ values change, all other cells
whose values depend on the changed values
(through a formula like this one) are changed
themselves, entirely automatically.
For example, suppose we find that Adams should
have gotten 85 rather than 81 on the final exam. As
soon as we edit the value in cell D6 to make it 85,
the spreadsheet looks like this:

Adams’ overall score is automatically
increased from 88.0 to 90.0 by Excel.
Now, what about those $ signs?
 Suppose we look at how Baker’s overall
score is computed by making C7 the active
cell:

What we see in the formula bar in this case
is:
=$B$4*B7+$C$4*C7+$D$4*D7
 This differs from the formula found in cell
E6 by using the corresponding values from
row 7 rather than row 6. That is, to compute
Baker’s overall score, we obviously want to
use Baker’s three test results, not Adams’s.

Likewise, for each student, a slightly
different formula must be used, taking into
account the values in the row representing
that particular student’s test scores.
 Does this mean the user must enter a
different formula for each student?
 No, because of the notion of relative vs.
absolute cell references.


In the formula
=$B$4*B6+$C$4*C6+$D$4*D6
the cell references B6, C6, and D6 are
relative, while the references to cells B4,
C4, and D4 are absolute. This is what the $
signs do – create an absolute cell reference.
When the formula
=$B$4*B6+$C$4*C6+$D$4*D6
is entered into cell E6, the reference to cell
B6, for example, is interpreted as “the cell 3
columns to the left of this cell and in the
same row.”
 Copying this formula to cell E7 then has the
same effect there, which amounts to
changing B6, C6, and D6 into B7, C7, and
D7, respectively.

A relative cell reference refers to a cell’s
location relative to the cell where the
formula is entered.
 The absence of a $ sign, as in B6, indicates
a relative reference.

On the other hand, in the formula
=$B$4*B6+$C$4*C6+$D$4*D6
the use of $ signs, as in $B$4, indicates an
absolute cell reference.
 No matter which cell this formula is entered
in, $B$4 always refers to the value in cell
B4.


In this particular example, this is what we
want because the cells B4, C4, and D4
contain the weightings to be applied in
computing the overall score for every
student.
Note that the $ sign precedes both the
column and row in an absolute reference.
 Another type of reference, called a mixed
reference, like $B4 or B$4, is also possible,
but it’s less commonly used and perhaps a
little more subtle to understand.
 (In fact, in this example, we’d still get the
right result if we used B$4, C$4, and D$4,
making only the row absolute.)

What makes spreadsheets
powerful
The use of formulas to allow automatic
calculation of some cells’ values in terms of
other cell’s values
 The use of relative (in addition to absolute)
cell references to allow essentially the
“same” formula to be used throughout the
spreadsheet.

Additional features of Excel
Ability to plot spreadsheet data easily using
a wide variety of graphical representations
(called charts in Excel).
 Large number of built-in mathematical
functions for use in cell formulas.
 Ability to solve equations and mathematical
optimization problems.
 Ability to use a spreadsheet like a simple
database and perform data analysis on it.

Excel terminology and basics
Excel uses the term worksheet to mean what
is more generally called a spreadsheet.
 Excel uses the term chart to mean any of
the possible graphs or charts that can be
created using Excel.
 The term workbook is then used to mean
any Excel file, which may contain several
worksheets and/or several charts.


You can enter and edit data on several
worksheets simultaneously and perform
calculations based on data from multiple
worksheets.
When you create a chart, you can place the
chart on the worksheet with its related data
or on a separate chart sheet.
 The names of the sheets appear on tabs at
the bottom of the workbook window.
 To move from sheet to sheet, click the sheet
tabs.
 The name of the active sheet is bold.

Names of worksheets
within a workbook.
What’s displayed vs. what’s
“really there”

Think of every cell in a worksheet as having
–
–
a surface layer, consisting of what’s displayed
for that cell; and
an underlying layer, consisting of either a
formula or internal representation of a constant
value.
If the underlying content of a cell is a
formula, the surface content is the computed
value, formatted according to the user’s
specifications.
 In our earlier example, cell E6 has as its
underlying contents the formula we gave, but
what is displayed on the worksheet is the
computed result of applying this formula. It is
also formatted to display the value to one
decimal place.


However, it is also possible to have the
formulas themselves displayed, rather than
the computed values, by checking the
appropriate box in the Tools => Options…
dialog box:
Even when the contents of a cell is a
constant, the value you see on the screen
depends on how you choose to format and
display the stored value.
 For example, a cell that displays a date as
"6/22/96" also contains a serial number that
is the underlying stored value for the date in
the cell.


You can change the surface display of the
date to another format (for example, to "22Jun-96"), but changing the surface display
of a value on a worksheet does not change
the underlying stored value.

Another example is the use of % format. In
the earlier sample worksheet, the contents
of cell B4 is displayed as 25%, but
internally it’s just the same as 0.25.