The concept of file name extensions did not originate as part of the file name itself, but rather as a separate attribute of the file. This concept can be traced back to the early days of machine-controlled mass storage, such as tape drives, where headers were used to describe how records were accessed within a file. As technology advanced and disks were introduced, more complex types were introduced. The naming convention for file extensions grew bottom-up, driven by the necessity to support file system services. The CTSS system took a different approach, providing a general-purpose field for marking purposes. This eventually led to the development of file extensions as we know them today. The DEC way of handling file extensions, using a dedicated field delimited by a dot, influenced systems like CP/M and MS-DOS. The Macintosh MFS and HFS took a unique approach with two file types noted in the file names, not visible to the user. The idea of putting information in file names only happened in systems based on a flat file concept. File extensions are not standalone file types but are used as a naming convention to structure a file name. Overall, the history of file extensions is complex and fascinating.
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