OpenOffice is an open-source, multiplatform and multilingual office suite comparable with MS Office. It is compatible with all other major office suites and is free to download, use, and distribute. It was previously known as StarOffice before it became an open-source project. OpenOffice comes with OpenWriter - a word processor, OpenCalc - a spreadsheet and OpenImpress - a presentational package. Is very good and offers many improvements.You may download Version 2 completely free of any licence fees, use it for any purpose - private, educational, government and public administration, commercial - and pass on copies free of charge to family, friends, students, employees, etc. The version offered for download here is the Windows version. Versions for other platforms are available from developer site.

       
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Very good text editor similar with Microsoft Office. Is a free spreadsheet application, a very good alternative for Microsoft Office.You can manage Excel,CSV,Word files etc with this free download.Was developer by Sun Microsystems.
OpenOffice.org Calc offer you help tutorials.
Menu for .ods extensions (related to Office Excel):
1.File
With File you can:
a) add new text document,spreadsheet,presentation,drawing,database,HTML document etc.
b) open new documents or recent spreadheets
c) Save instant or Save as (.ods mean OpenDocument spreadsheet, .ots , .sxc, .xls, .vor template etc)
d) export,export as a pdf,send document by email,print,preview print.
2.Edit
OpenOffice edit contains undo,redo,cut,copy,paste,find ,fill and plug-ins. File and Edit are the most used main menu .
3.View
View attribute allow to see with zoom (larger or smaller documents sizes),switch to full screen mode and taskbars enable (font work,insert cell,insert objects,text formatting,formula bar etc)
4.Insert
With Insert option can insert in a .ods document cells,rows,columns,pictures,special characters and charts
5.Format
Can format sheets (rows and cells), adjust flip,alignment and styles.Can merge cells , like Excel spreadsheet program.
6.Tools
A good category were Sun Microsystems allow to spellcheck,autocorrect set XML settings and autocalculator .
7.Data
On Data you define the range ,sort by a number of parameters,calculate subtotals and instert filters for columns in spreadsheets.
8.Window
- open new window
9.Help
Contain support ,help and registratin details.

OpenDocument Text (similar with Office Word) have the extension .odt.In Open Office Presentation you can import template or open an existing presentation..Select the slide design and preview before next step;choose the effect and speed for sheets presentation and press Create button. A nice .odp (open document presentation )page will appear.In the right you have the tasks and the sheets in miniature.Can configure the slide sorter,outline and notes.Can exchange background page on OpenOffice or delete background.
Can create database , open and edit an existing database or connect to another .Has a functions wizard . The functions (formulas) are in the left side and in the right you have a short presentation for every function who is selected .