File Extension
noun
say it: “FILE ek-STEN-shun” /faɪl ɪkˈstɛnʃən/
The letters after the last dot in a file name, such as .cs or .png, that tell the computer what kind of file it is.
What is File Extension?
File Extension — The letters after the last dot in a file name. They tell Windows, and you, what kind of file it is and which app opens it: Program.cs is C# code, menu.txt is plain text and logo.png is a picture. File Explorer hides them until you turn on View → Show → File name extensions.
In a sentence
- “Windows opened my notes in the wrong app because I saved them with a .cs file extension instead of .txt.”
Level: Novice · More Operating System terms at this level
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