Spreadsheet

Related Topics:
Spreadsheet :: Spreadsheets

A spreadsheet is a rectangular table (or grid) of information, often financial information. The word came from "spread" in its sense of a newspaper or magazine item (text and/or graphics) that covers two facing pages, extending across the center fold and treating the two pages as one large one. The compound word "spread-sheet" came to mean the format used to present bookkeeping ledgers -- with columns for categories of expenditures across the top, invoices listed down the left margin, and the amount of each payment in the cell where its row and column intersect -- which were traditionally a "spread" across facing pages of a bound ledger (book for keeping accounting records) or on oversized sheets of paper ruled into rows and columns in that format and approximately twice as wide as ordinary paper.

History

One of the first commercial uses of computers was in processing payroll and other financial records, so the programs (and, indeed, the programming languages themselves) were designed to generate reports in the standard "spreadsheet" format bookkeepers and accountants used. As computers became more available and affordable in the last quarter of the 20th century, more software became available for them, and programs to keep financial records and generate spreadsheet reports were always in demand. Those spreadsheet programs can be used to tabulate many kinds of information, not just financial records, so the term "spreadsheet" has developed a more general meaning as information presented in a rectangular table, usually generated by a computer.

The concept of an electronic spreadsheet was outlined in the 1961 paper "Budgeting Models and System Simulation" by Richard Mattessich. Some credit for the computerized spreadsheet perhaps belongs to Rene K. Pardo and Remy Landau, who filed a patent (U.S. Patent no. 4,398,249) on some of the related algorithms in 1970. While the patent was originally rejected by the patent office as being a purely mathematical invention, Pardo and Landau won a court case establishing that "something does not cease to become patentable merely because the point of novelty is in an algorithm." This case helped establish the viability of software patents.

The generally recognized inventor of the spreadsheet as a commercial product for the personal computer is Dan Bricklin although a fully interactve implementation produced in the United Kingdom at Imperial Chemical Industries running on an IBM mainframe platform pre-dated his version by several years even featuring shared public spreadsheets from the outset.

Bricklin has spoken of watching his university professor create a table of calculation results on a blackboard. When the professor found an error, he had to tediously erase and rewrite a number of sequential entries in the table, triggering Bricklin to think that he could replicate the process on a computer, using the blackboard as the model to view results of underlying formulas. His idea became VisiCalc, the first application that turned the personal computer from a hobby for computer enthusiasts into a business tool.

VisiCalc went on to become the first "killer app", an application that was so compelling, people would buy a particular computer just to own it. In this case the computer was the Apple II, and VisiCalc was no small part in that machine's success. The program was later ported to a number of other early computers, notably CP/M machines, the Atari 8-bit family and various Commodore platforms. Nevertheless, VisiCalc remains best known as "an Apple II program".

The introduction of the IBM PC in 1982 was initially fairly unsuccessful, as most of the programs available for it were ports from other 8-bit platforms. Things changed dramatically with the introduction of Lotus 1-2-3, which became that platform's killer app, and drove widespread sales of the PC due to the massive improvements over the VisiCalc port on the same platform. VisiCorp never responded in any convincing fashion, and disappeared within a few years.

Lotus 1-2-3 underwent an almost identical cycle with the introduction of Windows 3.x in the late 1980s. Microsoft had been developing Excel on the Macintosh platform for several years at this point, and it had developed into a fairly powerful system. A port to Windows 3.1 resulted in a fully-functional Windows spreadsheet which quickly took over from Lotus in the early 1990s. By the time Lotus responded with a usable Windows version of their own, Microsoft had started compiling their Office suite, which still dominates the industry..

A number of companies have attempted to break into the spreadsheet market with programs based on very different paradigms. Lotus introduced what is likely the most successul example, Lotus Improv, which saw some commercial success, notably in the financial world where its powerful data mining capabilities remain well respected to this day. Spreadsheet 2000 attempted to dramatically simplify formula construction, but was generally not successful. Stories attempted to make it easier to deal with 3-D blocks of data (as opposed to the 2-D nature of most spreadsheets), but appears to have seen little or no use.

Programming issues

Just as the early programming languages were designed to generate spreadsheet printouts, programming techniques themselves have evolved to process tables (also known as spreadsheets or matrices) of data more efficiently in the computer itself.

Spreadsheets have evolved into powerful programming languages, specifically, they are functional, visual, and multiparadigm languages. Spreadsheets qualify as programming languages because all or most of them are Turing complete.

Many people find it easier to perform calculations in spreadsheets than by writing the equivalent sequential program. This is due to two traits of spreadsheets.

They use spatial relationships to define program relationships. Like all animals, humans have highly developed intuitions about spaces, and of dependencies between items. Sequential programming usually requires typing line after line of text, which must be read slowly and carefully to be understood and changed.
They are forgiving, allowing partial results and functions to work. One or more parts of a program can work correctly, even if other parts are unfinished or broken. This makes writing and debugging programs much easier, and faster. Sequential programming usually needs every program line and character to be correct for a program to run. One error usually stops the whole program and prevents any result.

A spreadsheet program is designed to perform general computation tasks using spatial relationships rather than time as the primary organizing principle. Many programs designed to perform general computation use timing, the ordering of computational steps, as their primary way to organize a program. A well defined entry point is used to determine the first instructions, and all other instructions must be reachable from that point.

In a spreadsheet, however, a set of cells is defined, with a spatial relation to one another. In the earliest spreadsheets, these arrangements were a simple two-dimensional grid. Over time, the model has been expanded to include a third dimension, and in some cases a series of named grids. The most advanced examples allow inversion and rotation operations which can slice and project the data set in various ways.

The cells are functionally equivalent to variables in a sequential programming model. Cells often have a formula, a set of instructions which can be used to compute the value of a cell. Formulas can use the contents of other cells or external variables such as the current date and time. It is often convenient to think of a spreadsheet as a mathematical graph, where the nodes are spreadsheet cells, and the edges are references to other cells specified in formulas. This is often called the dependency graph of the spreadsheet. References between cells can take advantage of spatial concepts such as relative position and absolute position, as well as named locations, to make the spreadsheet formulas easier to understand and manage.

Spreadsheets usually attempt to automatically update cells when the cells on which they depend have been changed. The earliest spreadsheets used simple tactics like evaluating cells in a particular order, but modern spreadsheets compute a minimal recomputation order from the dependency graph. Later spreadsheets also include a limited ability to propagate values in reverse, altering source values so that a particular answer is reached in a certain cell. Since spreadsheet cells formulas are not generally invertable, though, this technique is of somewhat limited value.

Many of the concepts common to sequential programming models have analogues in the spreadsheet world. For example, the sequential model of the indexed loop is usually represented as a table of cells, with similar formulas. Cyclic dependency graphs produce the traditional construct known as the infinite loop. Most spreadsheets allow iterative recalculation in the presence of these cyclic dependencies, which can be either directly controlled by a user or which stop when threshold conditions are reached.

Shortcomings

While extremely popular, spreadsheets are not without their downsides. Some of the problems associated with spreadsheets include:

Lack of auditing and revision control. This makes it difficult to determine who changed what and when. This can cause problems with regulatory compliance, among other things.
Lack of security. Generally, if one has permission to open a spreadsheet, one has permission to modify any part of it. This, combined with the lack of auditing above, can make easy for someone to commit fraud.
Lack of concurrency. Unlike databases, spreadsheets typically allow only one user to be making changes at any given time.
Because they are loosely structured, it is easy for someone to introduce an error, either accidentally or intentionally, by entering information incorrectly or in the wrong place.

While there are built-in and third-party tools for desktop spreadsheet applications that address some of these shortcomings, awareness of these is generally low, and usage lower still. It should be noted, however, that many of these shortcomings can be handled by online spreadsheets like Google Spreadsheets and EditGrid.

References

External links

General information

A Brief History of Spreadsheets by D.J. Power
A Spreadsheet Programming article on DevX
comp.apps.spreadsheets FAQ by Russell Schulz
Extending the Concept of Spreadsheet by Jocelyn Paine
Develop Training Simulations with Excel
Linux Spreadsheets by Christopher Browne; much general information on spreadsheets, and some on related Linux issues
Software Arts and VisiCalc, by Dan Bricklin
Spreadsheet - Its First Computerization (1961-1964) by Richard Mattessich
"Spreadsheet Wars" - A classic video showing spreadsheet vendors going head-to-head in the late 80's .

Research organisations

European Spreadsheet Risks Interest Group (EuSpRIG)

Business software | Spreadsheets | Functional languages | Visual programming languages

Gourt Home::Gourt :: Spreadsheet