Microsoft Excel, the spreadsheet software developed and commercialized by Microsoft, is part of the Office Suite and it is available both for Macintosh systems and Windows. Originally designed to work on Macintosh systems, Excel had been ported to MS/DOS in 1987 due to the slow porting of Lotus 1-2-3 to the Microsoft operating system and since then it has been improved in its features, dominating the commercial spreadsheet market.
Excel can be installed both as a stand-alone application and as a part of Office Suite, offering in the latter case full integration with Word, PowerPoint and Publisher. Excel offers basic functions for data manipulation, like arithmetic operations and formulas, as well as embedded statistical functions, charts, graphs and histograms. Macro functions, designed to handle more complex data processing, make use of Visual Basic for Applications, a subset of the famous scripting language developed by Microsoft. Such a offer of features conveniently answer to statistical, engineering and financial needs, making Microsoft Office a first pick in the great variety of spreadsheet applications today available in the market.
What makes competitors a viable alternative is the pricing policy of Microsoft. Microsoft won't let you buy Excel as a stand-alone application. The software is sold as a part of the Microsoft Office Suite, offered at 149$ per license in the Home and Student version, 279$ for Home and Business version and 399$ for the Professional Suite. For people finding such prices impossible to afford it is necessary to move to cheaper reliable solutions, like OpenOffice.org suite, which features Calc as spreadsheet software.
OpenOffice.org is a complete suite, offering word processing, presentations and publishing as well as his famous spreadsheet application, Calc. Developed by Oracle, it can be freely downloaded and installed on Windows, Linux and MAC OS X, as well as on other operating systems on which Office is not able to run. While the huge different in price could make somebody think that Calc is not a viable alternative to Office, Oracle's spreadsheet features all the functionalities provided by Office: basic arithmetic operations, statistics, histograms and graphs, as well as being able to read and write in Microsoft formats like .xls, .doc and .ppt. Quick answers to your problems will be provided by the documentation provided by developers and users and it's possible to get direct and personal help from the Free Software/Open Source community, which is directly active in the development of the software.
As we just said, there are viable alternatives to reliable but expensive applications like Excel, keeping in mind that moving to a new platform is an investment in time, and hence, money. OpenOffice.org offers a good and cheap alternative, especially after the introduction of full compatibility with Microsoft most used formats. In business world, no matter how small your business is, being able to edit a .doc file makes the difference.