1.2 Compatibility with Microsoft Excel

SpreadScript is based on the NExS 1.4 spreadsheet, and supports all the native features and functions of that product. SpreadScript also supports a large subset of the most commonly used features of Excel. The following is a partial list of Excel features that are not supported:

• Visual Basic macros, embedded scripts, or any other VB features;
• OLE embedded documents (e.g., a Microsoft Word document embedded in an Excel spreadsheet);
• charts (currently they are skipped when reading in an Excel file);
• named formulas;
• Excel has some built-in functions that SpreadScript does not have, and SpreadScript has some functions not supported by Excel;
• ``3-D'' spreadsheet formulas and ranges are not supported (i.e., formulas and ranges that reference other sheets or a range of sheets); we are working on implementing support for this, as we already support multiple worksheets per workbook;
• password-protected workbooks;
• array references and functions.

By default, SpreadScript generates an exception when reading or writing Excel files with unsupported features. There are many times when the unsupported features, such as charts, are safe to skip. To have SpreadScript print an error message on standard error and continue rather than generate an exception, call stopOnExcelWarning(0) before reading or writing Excel spreadsheets. Carefully check the results to make sure that data integrity is not adversely affected.

SpreadScript includes an Excel compatibility mode, which allows formulas and function names to be entered exactly as they would be in Excel. Details on Excel compatibility mode are provided in Section 3.2.1.

When not operating in Excel compatbility mode, SpreadScript formulas use the NExS operator set, which includes all of operators in the C programming language (except auto-increment and auto-decrement), plus ``exponent'' and ``percent'' operators. This is a superset of the operators supported by Excel, with a few syntactic differences. For example, the exponent operator in Excel is a caret (^), and in NExS it is a double-asterisk (**). This is because the caret is used for the bit-wise exclusive OR operator in NExS, for which there is no equivalent operator in Excel. Differences between the SpreadScript and Excel formula syntax are fully described in Chapter 3.

To provide maximum compatibility with the installed base of Excel users, SpreadScript produces Excel ``.xls'' files in Excel 95 (BIFF7) format. This format can be read by all versions of Excel from Microsoft Office 95 forward. The Excel 95 file format limits the number of rows in a worksheet to 16,384 and and limits to 255 characters the length of string in a cell. SpreadScript reads Excel 95, 97, 2000, and 2002 (XP) file formats. Table 1.1 lists some of the key differences in limits of SpreadScript and Excel.

Table 1.1: Various limits of SpreadScript and Excel

	SpreadScript	Excel 95	Excel 97/2000/2002
Rows	32,768	16,384	65,536
Columns	4,096	256	256
Total cells in a worksheet	134,213,632	4,194,304	16,777,216
Length of string in a cell	4,095	255	32,767