Data Interchange Format
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Data Interchange Format (.dif) is a text file format used to import/export single spreadsheets between spreadsheet programs (OpenOffice.org Calc, Excel, Gnumeric, StarCalc, Lotus 1-2-3, FileMaker, dBase, Framework, Multiplan, etc.). It is also known as "Navy DIF". One limitation is that DIF format cannot handle multiple spreadsheets in a single workbook.
DIF was developed by Software Arts, Inc. (the developers of the VisiCalc program) in the early 1980s. The specification was included in many copies of VisiCalc, and published in Byte Magazine. Bob Frankston developed the format, with input from others, including Mitch Kapor, who helped so that it could work with his VisiPlot program. (Mitch later went on to found Lotus and make Lotus 1-2-3 happen.) The specification was copyright 1981.
DIF was a registered trademark of Software Arts Products Corp. (a legal name for Software Arts at the time).
DIF stores everything in an ASCII text file to mitigate many cross-platform issues back in the days of its creation. However modern spreadsheet software, e.g. OpenOffice.org Calc and Gnumeric, offer more character encoding to export/import. The file is divided into 2 sections: header and data. Everything in DIF is represented by a 2- or 3-line chunk. Headers get a 3-line chunk; data, 2. Header chunks start with a text identifier that is all caps, only alphabetic characters, and less than 32 letters. The following line must be a pair of numbers, and the third line must be a quoted string. On the other hand, data chunks start with a number pair and the next line is a quoted string, or one of the constants V (value), NA (not available), ERROR, TRUE, FALSE.
For example, assume we have two columns with one column header row and two data rows:
|has a double quote " in text||-3|
In a .dif file, this would be
TABLE 0,1 "EXCEL" VECTORS 0,2 "" TUPLES 0,3 "" DATA 0,0 "" -1,0 BOT 1,0 "Text" 1,0 "Number" -1,0 BOT 1,0 "hello" 0,1 V -1,0 BOT 1,0 "has a double quote "" in text" 0,-3 V -1,0 EOD
- Jeff Walden: File Formats for Popular PC Software. John Wiley & Sons, Inc., 1986. ISBN 0-471-83671-0
- Comment from Dan Bricklin, one of the developers of VisiCalc, on the discussion page of this article