.XLS

Introduction

BIFF5 is the workbook format of Excel 5.0, released in 1993, and Excel 95. It was the first Excel format to hold several sheets in one workbook file, stored inside a compound file. Excel 97 replaced it with BIFF8 but kept an option to save in it, often labelled “Microsoft Excel 5.0/95 Workbook”.

Text is stored in single-byte characters of a Windows code page, written into each cell’s record.

Structure

The file is a compound file, which starts with the signature D0 CF 11 E0 A1 B1 1A E1, holding a stream named Book. The stream is a sequence of records, each a 2-byte type, a 2-byte length and the data, all little-endian. It starts with the workbook globals: a BOF record (type 0x0809, version 0x0500), fonts, formats, cell styles and one BOUNDSHEET record per sheet giving its name and the offset of its records, ending with an EOF record. Each sheet follows as its own BOF to EOF block of row and cell records; text cells use LABEL records that carry the text itself.

Links