Quattro Pro is a spreadsheet program developed by Borland and now sold by Corel, most often as part of Corel's WordPerfect Office. Historically, Quattro Pro used keyboard commands similar to Lotus 1-2-3. It is commonly said to have been the first program to use tabbed sheets. Actually, Boeing Calc had tabbed sheets earlier. It currently runs under the Windows operating system. Quattro Pro avoided the 65,536 row by 256 column spreadsheet limitations inherent to pre-2007 versions of Microsoft Excel by allowing a maximum worksheet size of one million rows by 18,276 columns. Since about 1996 Quattro Pro has run a distant second to Excel's market domination.