Do the files "lose" association (ie behavioural change), or are they ones that you have downloaded from the internet? When you download a file from the internet, the default behaviour of Mac OS is to treat it as a random binary file, unless you (or the application that you used for download) modify it.
PC Exchange (or any Mac utility that reads DOS physical media) looks at the filename extension and assigns it a Mac file type. If your file is called twaddle.rtf, the Mac OS will try to find an application that can read an RTF file to open the file.
In the early 1990s, independent developers conceived Internet Config (IC) for the Mac. When you downloaded a file from the internet, IC used the same tricks as PC Exchange to give it a Mac file type. IC has a control panel to configure file associations. Internet app developers worked with the IC team and eventually it became an Apple standard. The control panel in OS 9.x that assigns file associations is a daughter of IC -- and early versions of IC work on System 6.
To have file association on a Mac, you need to be running an INIT that handles internet downloads (IC or its successors) and a disk handler such as PC Exchange. A disk handler will convert filename extensions into useful associations if you insert a floppy disk or CD or Zip. If you are lucky a disk handler will cope with DOS files on an AppleShare volume. IC handles internet downloads and email attachments.
All the same, don't trust in Mac filename association mapping. If the file has a blank icon and you think that it is a valid Excel or HTML file, try opening it from a suitable application.
If you download FileX using Mac OS X or Windows or Linux, the OS will have a go at understanding FileX; FileX.doc will open in the application assigned for Word documents. You can pass that file between loads of computers and the odds are that the OS or applications will assume that it is an MS Word document. That applies to many different filename extensions.
Try the same with FileX.sit.hqx, a standard compression plus encoding for a vintage Mac file. If you download FileX.sit.hqx, a contemporary computer may treat it as a random binary or text file, or it may attempt to process it with various degrees of success. Then you, using the wonders of networks or physical media, transfer it to your vintage Mac. At that point, you may have something with a blank icon called FileX, FileX.sit or FileX.sit.hqx on your vintage Mac disk.
If it is called FileX.sit or FileX.sit.hqx, ignore the blank icon and use your favourite sit and hqx processors to unravel the file. If it is called FileX and is completely useless, return to the computer that you used for the initial download. Make copies of FileX.sit.hqx called FileX.sit.txt and FileX.sit.xxx, then repeat the file transfer process to the vintage Mac.
The version called FileX.sit.txt should have been treated as an ASCII text file during transfers. Rename it as FileX.sit.hqx and try to unpack it.
The version called FileX.sit.xxx should have been treated as a binary file during transfers. Rename it as FileX.sit.hqx and try to unpack it.
If you are still struggling, try a few files from different sites. Your problems may be more complex than unpacking files based on filename extension.
And if you are downloading loads of files that cannot be identified after trying all of the above, test out one of the utilities that assigns file mapping post download. I'll leave it to others to suggest.
PC Exchange (or any Mac utility that reads DOS physical media) looks at the filename extension and assigns it a Mac file type. If your file is called twaddle.rtf, the Mac OS will try to find an application that can read an RTF file to open the file.
In the early 1990s, independent developers conceived Internet Config (IC) for the Mac. When you downloaded a file from the internet, IC used the same tricks as PC Exchange to give it a Mac file type. IC has a control panel to configure file associations. Internet app developers worked with the IC team and eventually it became an Apple standard. The control panel in OS 9.x that assigns file associations is a daughter of IC -- and early versions of IC work on System 6.
To have file association on a Mac, you need to be running an INIT that handles internet downloads (IC or its successors) and a disk handler such as PC Exchange. A disk handler will convert filename extensions into useful associations if you insert a floppy disk or CD or Zip. If you are lucky a disk handler will cope with DOS files on an AppleShare volume. IC handles internet downloads and email attachments.
All the same, don't trust in Mac filename association mapping. If the file has a blank icon and you think that it is a valid Excel or HTML file, try opening it from a suitable application.
If you download FileX using Mac OS X or Windows or Linux, the OS will have a go at understanding FileX; FileX.doc will open in the application assigned for Word documents. You can pass that file between loads of computers and the odds are that the OS or applications will assume that it is an MS Word document. That applies to many different filename extensions.
Try the same with FileX.sit.hqx, a standard compression plus encoding for a vintage Mac file. If you download FileX.sit.hqx, a contemporary computer may treat it as a random binary or text file, or it may attempt to process it with various degrees of success. Then you, using the wonders of networks or physical media, transfer it to your vintage Mac. At that point, you may have something with a blank icon called FileX, FileX.sit or FileX.sit.hqx on your vintage Mac disk.
If it is called FileX.sit or FileX.sit.hqx, ignore the blank icon and use your favourite sit and hqx processors to unravel the file. If it is called FileX and is completely useless, return to the computer that you used for the initial download. Make copies of FileX.sit.hqx called FileX.sit.txt and FileX.sit.xxx, then repeat the file transfer process to the vintage Mac.
The version called FileX.sit.txt should have been treated as an ASCII text file during transfers. Rename it as FileX.sit.hqx and try to unpack it.
The version called FileX.sit.xxx should have been treated as a binary file during transfers. Rename it as FileX.sit.hqx and try to unpack it.
If you are still struggling, try a few files from different sites. Your problems may be more complex than unpacking files based on filename extension.
And if you are downloading loads of files that cannot be identified after trying all of the above, test out one of the utilities that assigns file mapping post download. I'll leave it to others to suggest.