What Is a Computer File?

Lisa Bigelow
Lisa Bigelow

A computer file is a storage unit that is held on a computer’s operating system. This storage unit could be a document, an image, a video, or an application. Users can open files, review and change their contents, and then save and close them, using the same or different file name.

With the right software, you can create, edit, and save files on your computer.
With the right software, you can create, edit, and save files on your computer.

A computer file is made up of a name that creates the file’s identity and an extension that tells the operating system and associated programs what type of file it is. For example, a file named “Budget.xls” tells the user – and the operating system – that the document is an Excel program. “Budget” is the file identity and “xls” is the file extension.

A file folder can contain files, other folders, or nothing at all.
A file folder can contain files, other folders, or nothing at all.

Most common files are made up of a name and an extension. Originally, the name of a file was limited to eight characters, but modern systems allow for much longer file names. The name is generally determined by the user or associated program and often gives an indication of the file’s purpose.

You can transfer files between computers and devices with a dongle.
You can transfer files between computers and devices with a dongle.

What are the types of computer files?

Basic file types include database, document, presentation, and worksheet. Other types of files include program files and system files. Programs are executable files and system files aren’t opened or modified, but help your computer run its operating system.

The file extension tells the user and the computer what type of file it is. Documents, images, and videos are common file types.
The file extension tells the user and the computer what type of file it is. Documents, images, and videos are common file types.

Did You Know?

  • A computer file is a basic storage unit.
  • File types include documents, images, videos, and MP3s, but they also include programs and other files that help your computer’s operating system run smoothly.
  • Files are stored in folders. Folders can contain many different files or can be empty. Folders can also store other folders (called “subfolders”).
  • The file extension tells the user and the computer’s operating system what type of file it is.

What does “file extension” mean?

The file extension identifies the file type to the user and the computer’s operating system and appears after the filename and a period. Common file extensions include JPG, PNG, XLS, DOC, PDF, and PPT, although there are many others, such as WMV and EXE.

A file’s extension is typically a period followed by two to four characters. This part of the filename is used by the operating system for internal cataloging. The way an extension is used varies between operating systems; some require the extension and some completely ignore it. Most systems fall in between – the extension helps identify the programs used with the file and acts as a shortcut when read.

The data in a computer file is complete and whole. The information within a file may be opened, read, modified, and saved, given the proper software. The information contained within the file may require other information to operate, such as an executable file needing a database file to properly execute, but the executable and database files are two separate files.

What’s the difference between a file and a file folder?

A computer folder, which is sometimes called a “directory,” stores computer files. Although a file is always stored in a folder, a folder doesn’t need to contain any files and is sometimes empty.

Interestingly, some modern programs that you may think of as files are actually folders. Microsoft programs later than 2007, including Excel, Powerpoint, and Word (with the XLSX, DOCX, and PPTX file extensions), are actually folders.

How do I set up a file system on a computer?

Some file systems are already installed when you buy your computer, such as program files and system files. But you can arrange your own folder hierarchy for basic file types however you like, typically by dragging and dropping documents and images into folders you create yourself.

A folder hierarchy is a visual representation of how folders and subfolders are organized. You can include multiple file extensions in one folder; for example, you can include XLS, DOC, PPT, WMV, PDF, and JPG in one folder.

Can I transfer a file to another computer?

Yes, but you may not be able to open, read, or modify the file if the new computer doesn’t have the proper hardware installed.

There are multiple ways to transfer files. For example, you can transfer files using an external hard drive or through the web. But you’ll need to have the executable program file installed before you can open, read, and modify (and save) the file.

What else should I know about computer files?

Since each computer file is distinct to itself, there are certain characteristics that are common between any type of file.

Every file has a size, even if that size is zero. The information stored within the file requires a location on the computer system, so each file is indexed by the system. Lastly, every file contains attributes that determine its use. These attributes, like who may open or alter a file or whether the file may be seen by normal users, are built into the structure of the file, not its internal data.

The last aspect of every computer file is that they exist in some way on the computer system. A computer file may be created or deleted, moved or copied, or altered. A user may do this by using programs associated with those files or through the file management of the operating system itself. These operations may be difficult with some files due to their interaction with the operating system, but it still may be done.

Powerpoint is a common computer file type.
Powerpoint is a common computer file type.
Lisa Bigelow
Lisa Bigelow
Lisa Bigelow writes for Bold and is an award-winning content creator, personal finance expert, and mom of three fantastic almost-adults. Lisa has contributed to MagnifyMoney, FinanceBuzz, Life and Money by Citi, Well + Good, Smarter With Gartner, and Popular Science. She lives with her family in Connecticut.

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Discussion Comments


Computer file recovery can be an effective technique in recovering those files you’ve accidentally deleted. The deleted files are in one partition of the hard disk and the recovery software searches that location to recover the files. Some scientists have even developed algorithms to recover files once thought to be permanently scrubbed, but I don’t know how effective those techniques are.


Most operating systems will look at the computer file extension to determine what kind of file it is. Some files are executable files (they end with the .exe, .com or .bat extensions) while other files are text files, spreadsheet files or other files meant to be read and interpreted by some program. With Windows, double-clicking on the executable files will immediately run those files.

This can be a double-edged sword if those files contain viruses. That’s why it’s best if you get file attachments that you’re not sure about, don’t double-click them. That will immediately launch them and the viruses will run. At best, rename the file extension to something like “.txt” or something that the computer won’t try to run automatically. Of course the best policy is just to delete those attachments that you’re suspicious of.

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