BOF: Beginning of File (809h)

The BOF record marks the beginning of the Book stream in the BIFF file. It also marks the beginning of record groups (or "substreams" of the Book stream) for sheets in the workbook. For BIFF2 through BIFF4, you can determine the BIFF version from the high-order byte of the record number field, as shown in the following table. For BIFF5/BIFF7, and BIFF8 you must use the vers field at offset 4 to determine the BIFF version.

BOF Record Number Field

Offset	Name	Size	Contents

0	vers	1	version: = 00 BIFF2 = 02 BIFF3 = 04 BIFF4 = 08 BIFF5/BIFF7/BIFF8
1	bof	1	09h

Record Data — BIFF8

Offset	Name	Size	Contents

4	vers	2	Version number: = 0600 for BIFF8
6	dt	2	Substream type: 0005h = Workbook globals 0006h = Visual Basic module 0010h = Worksheet or dialog sheet 0020h = Chart 0040h = Microsoft Excel 4.0 macro sheet 0100h = Workspace file
8	rupBuild	2	Build identifier (=0DBBh for Microsoft Excel 97)
10	rupYear	2	Build year (=07CCh for Microsoft Excel 97)
12	bfh	4	File history flags
16	sfo	4	Lowest BIFF version (see text)

The rupBuild and rupYear fields contain numbers that identify the version (build) of Microsoft Excel that wrote the file. If you write a BIFF file, you can use the BiffView utility to determine the current values of these fields by examining a BOF record in a workbook file.

The sfo field contains the earliest version (vers field) of Microsoft Excel that can read all records in this file.

The bfh field contains the following flag bits:

Bits	Mask	Name	Contents

0	00000001h	fWin	= 1 if the file was last edited by Microsoft Excel for Windows
1	00000002h	fRisc	= 1 if the file was last edited by Microsoft Excel on a RISC platform

Bits	Mask	Name	Contents

2	00000004h	fBeta	= 1 if the file was last edited by a beta version of Microsoft Excel
3	00000008h	fWinAny	= 1 if the file has ever been edited by Microsoft Excel for Windows
4	00000010h	fMacAny	= 1 if the file has ever been edited by Microsoft Excel for the Macintosh
5	00000020h	fBetaAny	= 1 if the file has ever been edited by a beta version of Microsoft Excel
7 – 6	000000C0h	(Reserved)	Reserved; must be 0 (zero)
8	00000100h	fRiscAny	= 1 if the file has ever been edited by Microsoft Excel on a RISC platform
31 – 9	FFFFFE00	(Reserved)	Reserved; must be 0 (zero)

Record Data — BIFF5 and BIFF7

Offset	Name	Size	Contents

4	vers	2	Version number (0500 for BIFF5 and BIFF7)
6	dt	2	Substream type: 0005h = Workbook globals 0006h = Visual Basic module 0010h = Worksheet or dialog sheet 0020h = Chart 0040h = Microsoft Excel 4.0 macro sheet 0100h = Workspace file
8	rupBuild	2	Build identifier (internal use only)
10	rupYear	2	Build year (internal use only)