Commonly Used Computer File Formats There are different file types with their own format for different purposes. To open and see inside a file you need the right program installed on your computer. The format of a file is shown by the 3 or 4 letter suffix (also called the filename extension). Here is a short list of the more commonly used file formats: Suffix Type of Fie Suitable Programs .doc WORD documents, old format Microsoft WORD LibreOffice WRITER .docx WORD documents, new format Microsoft WORD 2007 or later LibreOffice WRITER .xls EXCEL spreadsheet, old format Microsoft EXCEL LibreOffice CALC .xlsx EXCEL spreadsheet, new format Microsoft EXCEL 2007 or later LibreOffice CALC .pdf ADOBE portable document format Adobe Reader (for reading only, not creating) Most browsers such as Firefox, Chrome etc. LibreOffice .jpg Digital photographs Picasa Most browsers, such as Firefox, Chrome etc. Photoshop .txt Plain text file Microsoft WORD Microsoft NOTEPAD LibreOffice WRITER Most browsers such as Firefox, Chrome etc. .odt Open Document Format LibreOffice WRITER default .ods Open Spreadsheet Format LibreOffice CALC default .ppt Presentation, old format Microsoft POWERPOINT LibreOffice IMPRESS .pptx Presentation, new format Microsoft POWERPOINT 2007 or later LibreOffice IMPRESS .wps Microsoft Works document LibreOffice may make some sense of it - now obsolete You can download and install LibreOffice 4.1 here: http://www.libreoffice.org/download LibreOffice by default saves text documents as .odt files and spreadsheets as .ods files. Change these defaults on Windows via the Menu choice: Tools> Options> Load/Save> General e.g. change the default for Text Documents to the old Microsoft format, e.g. Word 97/2000/XP/2003 or the new Microsoft format, e.g. Word 2007/2010 XML Alan Jenyon July 2013.