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^C^1Introduction to Spreadsheets
^Cby
^CDaniel Tobias

   The concept of the computerized spreadsheet was originated in 1979 with the
release of VisiCalc for the Apple II computer.  This program became wildly
successful, topping the "Top Thirty" list of software programs for several years
straight.  It ultimately spawned hordes of imitators, many of which proved
superior to the original in functionality.  This ultimately proved the downfall
of VisiCorp (originally Personal Software; they had been a publisher of many
kinds of software, including some popular games, before they decided to
specialize in VisiCalc and related programs); they were unable to keep pace with
their competition, and ultimately went bankrupt.

   Although VisiCalc is dead, it has left behind a great legacy.  All electronic
spreadsheet software around today (including LOTUS 1-2-3 and its many "clones")
is derived ultimately from the concept pioneered in that original spreadsheet.

   A spreadsheet program is essentially a computerized version of the ledger
pages familiar to accountants.  These sheets have rows and columns on which you
can enter figures and headers, including special rows and columns intended to
contain totals of various other figures on the page.  As you enter data onto the
paper, you must manually calculate the totals, generally using a pocket
calculator.

   A computerized spreadsheet starts out similar to the paper sheets.  When you
start it running, you are presented with a screenful of empty boxes arranged in
rows and columns.  However, one difference from paper presents itself
immediately; you can use the arrows to scroll down or to the right from the
starting point (in the upper left corner), and thus expose the full extent of
the sheet in the computer's memory; while the size varies from program to
program, it usually extends to hundreds of rows and dozens of columns, much more
than will fit on a normal-sized sheet of paper.  Thus, you can fit very complex
sets of figures on one spreadsheet, where they would have to be spread out over
many pages on paper.  This is helpful in getting the "big picture" at once.

   However, the real power of a computerized spreadsheet does not show itself
until you set up calculations within the sheet.  Each cell can be filled with
any of several different things.  As with a paper sheet, you can enter a number
(such as a dollar amount) or text (such as the header at the top of a column).
However, there is a third type of entry that can't be done on paper:  you can
enter a formula based on other entries in the spreadsheet.  For instance, a cell
can contain the formula "100 * A2 / A3 + A4".  This represents the value in cell
A2 multiplied by 100, then divided by the value of cell A3, then added to the
value of cell A4.  When you type this formula in a cell, the computer will
calculate the value based on what is currently in cells A2, A3, and A4.  This
result will appear, just like magic, in the cell containing the formula, just
like you had typed the number there manually.

   What's more, if you then go to cells A2, A3, and A4, and alter the values
there, then the value of the formula cell will instantly change to reflect the
changes you have made.

   This has many applications.  You can set up a row at the bottom of the
spreadsheet that contains the totals of the figures in each column; this total
will always be kept up to date whenever you alter the figures, or add new rows
of figures.  You don't have to keep manually adding them.

   Also, if you'd like to play "What If" by altering some figures and seeing what
it does to the bottom line, you can set up appropriate formulas and experiment
all you wish, getting the instant gratification of seeing the results of each
experiment.  On a paper ledger sheet, you'd have to keep erasing figures, and
doing lengthy mathematical calculations; the computer does all that for you
automatically.  Cells referenced in a formula may contain ordinary numeric
values, or they may be formulas themselves; thus, you can have very complex
interrelationships among values.

   For instance, you can set up a number of cells representing different types of
expenditures and sources of income, and create formula cells to add them all up
and determine the amount and percentage of profit yielded.  Then, you can play
around with the figures (What if I lowered payroll expenses by 10 percent?) and
see how it affects the overall picture.  You can make the model as complex as
you wish, using figures that are dependent on a whole range of other figures
elsewhere in the spreadsheet.

   Spreadsheets were modeled after accounting ledger pages, and hence, the
intended applications generally involved financial calculations.  This is still
what spreadsheet programs are most often used for.  However, their applications
are limited only by your imagination.  You can set up mathematical problems of
any sort, whether they apply to finance, engineering, or whatever, using a
spreadsheet program.  Some have even set up games and puzzles on a spreadsheet;
several of the "Computer Recreations" columns appearing monthly in Scientific
American have been devoted to this topic.  I once saw an entire "blackjack" game
set up on a spreadsheet; it automatically dealt the cards through a series of
complicated formulas.  (This was done using a particularly powerful spreadsheet
program; most spreadsheets probably couldn't handle it.)

   Our special program this issue is ExpressCalc, an excellent "shareware"
spreadsheet.  Try it out, and see how spreadsheets can help you.

   A final note:  templates are files containing pre-arranged sets of formulas
that instruct a spreadsheet on how to do a task.  We are including several
templates for ExpressCalc.  Also, we are running a contest to let you design and
submit your own templates, and win cash prizes.  See the "Templates" menu item
for details.
