Files and Extensions

A file is a set of computer code (software) that contains all of the information necessary to complete a particular task.  There are different kinds (or types) of files, denoted by different extensions, which consist of a period followed by (usually) three letters that abbreviate the kind of the file.

Examples
Applications are files, and they are denoted by the .app extension on Mac OS X, and by the .exe extension on Windows (.exe stands for "executable file").  Other common files are Microsoft Word files, which contain whatever you wrote on Microsoft word.  These have the .doc and .docx extension (both stand for "document," but the x in .docx is to distinguish the newer version of Word from previous ones).  Here are some others:

• Microsoft Excel: .xls and .xlsx
• Microsoft PowerPoint: .ppt and .pptx
• MP3 and AAC (music files): .mp3 and .aac
• MPEG (video files): .m4p and .mp4
• Web Pages: .htm and .html
• Plain Text (i.e. without formatting like color, size, font): .txt
• JPEG, GIF, TIFF, RAW (images/pictures): .jpg, .gif, .tif, .raw
• PDF (Portable Document Format): .pdf

Tomorrow: Revisit some previous topics with our new tech-lingo