Why do computer files have extensions?
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Answer: Tell OS how to open files
Make filenames longer — Wrong. Extensions don't exist to lengthen names. They indicate file type, telling the operating system which application should open the file.
Tell OS how to open files ✓ — Correct! File extensions (.pdf,.jpg,.exe,.txt) tell the operating system what type of file it is and which application should open it..docx = Word document,.mp4 = video,.py = Python code. Extensions are associated with programs—double-clicking a.pdf opens your PDF reader. Some systems hide extensions but still use them internally!
Track file creation dates — Wrong. Extensions indicate file type/format, not dates. Metadata stores creation/modification times separately from the filename.