Lotus 4 Worksheet (.wk4)
The WK4 file extension, short for Lotus 4 Worksheet, was developed by IBM for its Lotus 1-2-3 spreadsheet software. These files store data in cells organized into rows and columns, similar to modern spreadsheets. Primarily used for data entry and accounting, WK4 files have become less common with the discontinuation of Lotus 1-2-3. While older versions of Microsoft Excel could import WK4 files, this support was dropped in Excel 2007 and later. Today, specialized converters or older spreadsheet programs like Gnumeric can still open WK4 files.