Sheet files start with a Header Section which starts with the following codes:

Offset Size Data Description

0000 ID 37 00 00 10 UID1: Header Section layout

0004 ID 6D 00 00 10 UID2: File kind

0008 ID 88 00 00 10 UID3: Application ID

000C L A8 15 08 55 UID4: Checksum of UID1,2 and 3

0010

The Section Table Section may contain the following sections, usual in the given order:

Identifier Section Always found

CD 00 00 10 Offset of the Password Section No

1F 01 00 10 Offset of the Sheet Status Section Yes

05 01 00 10 Offset of the Page Layout Section Yes

1D 01 00 10 Offset of Sheet Workbook Section Yes

21 01 00 10 Offset of the Sheet Graph List Section Yes

89 00 00 10 Offset of the Application ID Section Yes

The Password Section is only found in encrypted documents. At least the Sheet Graph List Section is encrypted if it is found.