BIFF3

BIFF3 refers to the third version of the Binary Interchange File Format (BIFF) used by Microsoft Excel to store spreadsheets in a binary file. Developed in the early 1990s, BIFF3 was employed by Excel 3.0 and early Excel 4.x for both Windows and DOS environments. It is part of the lineage of Excel’s native binary formats that preceded later versions such as BIFF4 and BIFF5.

The format is file-based and record-oriented. A BIFF3 file consists of a sequence of records, each beginning with a record type identifier and a two-byte length, followed by a payload. The file starts with a beginning-of-file (BOF) record and ends with an end-of-file (EOF) record. Common records handle workbook and sheet definitions, dimensions, and the storage of cell data, including rows, columns, and basic formatting information. The arrangement allows multiple worksheets within a single workbook and supports a range of data types and formatting options, though with the limitations of the era’s software.

Data stored in BIFF3 includes numeric and textual cell values, simple formulas, and basic formatting attributes such as font and alignment. The organization enables reading and writing of workbook structures, sheet data, and related metadata, using a compact binary representation optimized for the hardware of the time.

Legacy status and impact: BIFF3 is now considered obsolete, superseded by newer BIFF versions that introduced expanded capabilities and compatibility with evolving Excel features. Modern Microsoft Excel uses newer binary formats and the XML-based XLSX format, while BIFF3 remains of historical interest to researchers, archivists, and developers working with early Excel documents.