What is a File and What is the significance of file extension and file formats?

Answer 1

In computing, a file is simply any device which we can use to send and/or receive information. A printer is a file. A mass-storage device is a file. The internet is a file. Even the NUL device is a file. However, we commonly use the term to refer to the information itself rather than to the device. So in that sense, a file is simply data and, in most cases, that data will be stored on a mass-storage medium of some kind, typically a local hard-disk drive.

There are two types of file we can store on mass-storage mediums: files and folders. A folder is simply a file we can use to contain other files (including other folders). The root folder is the primary folder of the storage medium and is the only folder that has no name. All other files must be named such that they are unique to the folder that contains them.

The file name may include a file extension or suffix. The suffix may be any length but is typically three characters long and is always prefixed with a period. On some systems a filename may include two or more periods, however the final period always denotes the file extension. Some systems also allow a trailing period with no extension. The extension is considered part of the file name however the extension alone (including the prefix period) can be used to name a file on some systems.

The only purpose of the file extension is to associate a file with the application that uses that extension. For instance, we might choose to associate BMP files with Windows Paint, so if we double click a BMP file, Windows Paint will automatically execute and load the file for us. However, it's important to note that the file extension has no bearing on the actual file type. That is, changing the file extension won't change the file's type, it will simply change which program is associated with that file. Most complex file types will store the actual type within the file itself.