Early Microsoft Excel

The first version of Microsoft Excel was released on Macintosh in 1985. Before that there was MultiPlan.

The ancestor of Excel is Multiplan 1981-1988.
Until v4, it used blitted files.
From v4 on, it’s using Biff1, like Excel 1: Starts with 09 00 BoF, Ends with 0A 00 EoF.

Easter egg? Plan lives forever

— Ange (@angealbertini) March 12, 2023

MultiPlan version 4 and Excel version 2 used the well known and documented BIFF format. Before BIFF2 the formats are a bit of a mystery. AFAIK, Microsoft never released any documentation on the file format used for Excel version 1 and MultiPlan 1 -3, they emphasized using the SYLK format for interchange. To make matters worse, there were upwards of 100 different versions of the early MultiPlan, ported for dozens of different systems. Some of them are discussed on the TRS-80 website.

Or you can take MultiPlan 1.06 for a spin over at PCjs!

Needless to say documenting and finding a pattern which could be used to identify the early versions of MultiPlan and Excel 1 are difficult. These versions are missing from the PRONOM registry, but hopefully with enough samples, some patterns can be found to confidently identify formats from the early days of spreadsheets!

Marco Pontello’s TrID identifier software has signatures for the early Multiplan and Excel formats. His software scans for patterns in samples and finds commonalities between them. So the more samples he can scan the more accurate the identification can be.

Currently the signatures are as follows.

Microsoft Excel for Mac Spreadsheet (v1.x)
		<Pattern>
			<Bytes>532700</Bytes>
			<ASCII> S '</ASCII>
			<Pos>0</Pos>
		</Pattern>
		<Pattern>
			<Bytes>AB27000000000000000203</Bytes>
			<ASCII> . '</ASCII>
			<Pos>4</Pos>
		</Pattern>
Multiplan for Mac spreadsheet (v1.x)
		<Pattern>
			<Bytes>11AB000013E8000000000000</Bytes>
			<ASCII> . . . . . . . . . . . .</ASCII>
			<Pos>0</Pos>
		</Pattern>
Multiplan spreadsheet (v1.x)
		<Pattern>
			<Bytes>0CE9000008AB08001F0016000200</Bytes>
			<Pos>0</Pos>
		</Pattern>
Multiplan spreadsheet (v1.0x)
		<Pattern>
			<Bytes>08E700</Bytes>
			<Pos>0</Pos>
		</Pattern>
		<Pattern>
			<Bytes>0100</Bytes>
			<Pos>6</Pos>
		</Pattern>
		<Pattern>
			<Bytes>000000</Bytes>
			<Pos>11</Pos>
		</Pattern>
Multiplan spreadsheet (v2.x)
		<Pattern>
			<Bytes>0CEC000008AB08001F001A000300</Bytes>
			<Pos>0</Pos>
		</Pattern>
Multiplan for Xenix spreadsheet (v2.x)
		<Pattern>
			<Bytes>0AEC000008AB08001F001A000300</Bytes>
			<Pos>0</Pos>
		</Pattern>
Multiplan spreadsheet (v3.x)
		<Pattern>
			<Bytes>0CED000008AB08001F001A000000</Bytes>
			<Pos>0</Pos>
		</Pattern>

There seems to be some patterns between versions, but then also some major differences. Without a specification or an understanding of the system the samples were created on, it is hard to identify these formats with certainty. There could be hex values which are the same for the samples we have but different for others, headers can often have values indicating dates or length of the file, so finding variations in files is key to a good signature.

Keep an eye on my GitHub PRONOM Research folder as I add more samples and prepare a signature for PRONOM.