terminals. Over 150 copies were licensed (35 to Fortune 500 companies). DP managers were attracted to compatibility and avoiding then-expensive PC purchases (see 1983 Computerworld magazine front page article and advertisement.) Other spreadsheets Notable current spreadsheet software: Apache OpenOffice Calc is a free and open-source. Calligra Sheets (formerly KCalc) Collabora Online Calc for mobile and desktop apps are free, open-source, cross-platform enterprise-ready editions of LibreOffice. Corel Quattro Pro (WordPerfect Office) Gnumeric is free and cross-platform, it is part of the GNOME Free Software Desktop Project. Kingsoft Spreadsheets LibreOffice Calc is free, open-source and cross platform. NeoOffice Numbers is Apple Inc.'s spreadsheet software, part of iWork. PlanMaker (SoftMaker Office) Pyspread Discontinued spreadsheet software: 20/20 3D-Calc for Atari ST computers Framework by Forefront Corporation/Ashton-Tate (1983–84) GNU Oleo – A traditional terminal mode spreadsheet for UNIX/UNIX-like systems IBM Lotus Symphony (2007) Javelin Software KCells Lucid 3-D Lotus Improv Lotus Jazz for Macintosh Lotus Symphony (1984) MultiPlan Claris' Resolve (Macintosh) Resolver One Borland's Quattro Pro SIAG SuperCalc T/Maker Target Planner Calc for CP/M and TRS-DOS Trapeze for Macintosh Wingz for Macintosh Other products Several companies have attempted to break into the spreadsheet market with programs based on very different paradigms. Lotus introduced what is likely the most successful example, Lotus Improv, which saw some commercial success, notably in the financial world where its powerful data mining capabilities remain well respected to this day. Spreadsheet 2000 attempted to dramatically simplify formula construction, but was generally not successful. Concepts The main concepts are those of a grid of cells, called a sheet, with either raw data, called values, or formulas in the cells. Formulas say how to mechanically compute new values from existing values. Values are general numbers, but can also be pure text, dates, months, etc. Extensions of these concepts include logical spreadsheets. Various tools for programming sheets, visualizing data, remotely connecting sheets, displaying cells' dependencies, etc. are commonly provided. Cells A "cell" can be thought of as a box for holding data. A single cell is usually referenced by its column and row (C2 would represent the cell containing the value 30 in the example table below). Usually rows, representing the dependent variables, are referenced in decimal notation starting from 1, while columns representing the independent variables use 26-adic bijective numeration using the letters A-Z as numerals. Its physical size can usually be tailored to its content by dragging its height or width at