file type

file type: In the Windows environment, a designation of the operational or structural characteristics of a file. The file type identifies the program, such as Microsoft Word, that is used to open the file. File types are associated with a file name extension. For example, files that have the .txt or .log extension are of the Text Document type and can be opened using any text editor.

In the Macintosh environment, a four-character sequence that identifies the type of a Macintosh file. The Macintosh Finder uses the file type and file creator to determine the appropriate desktop icon for that file.