What Is Compatibility?

Compatibility is an oft-used term among computer people. In general, it refers to how well software performs under various conditions. These conditions might be defined in terms of hardware, software, or a combination of the two. For example, software that is written specifically for a 32-bit operating system such as Windows XP will not run under the older 16-bit versions of Windows 3. x . In other words, 32-bit applications are not compatible with Windows 3. x . And, as I'm sure you realize, software written for Windows will not run directly on other operating systems, such as Macintosh or Linux.

In this chapter, I discuss a more specific compatibility issue involving how your Excel 2007 applications will work with earlier versions of Excel for Windows and Excel for Macintosh. The fact that two versions of Excel might use the same file format isn't always enough to ensure complete compatibility between the contents of their files. For example, Excel 97, Excel 2000, Excel 2002, Excel 2003, and Excel 2002 for Macintosh all use the same file format, but compatibility issues are rampant. Just because a particular version of Excel can open a worksheet file or an add-in doesn't guarantee that that version of Excel can carry out the VBA macro instructions contained in it.

The past few releases of Excel have been relatively minor upgrades. Consequently, compatibility problems were minimal. The introduction of Excel 2007, however, greatly increases the number and types of potential compatibility problems. Besides using a new file format, Excel 2007 includes many new features that aren't available in earlier versions.

Excel is a moving target, and there is really no way that you can guarantee complete compatibility. Unfortunately, cross-version compatibility doesn't happen automatically. In most cases, you need to do quite a bit of additional work to achieve compatibility.