> A terminate-and-stay-resident program (commonly TSR) is a computer program running under DOS that uses a system call to return control to DOS as though it has finished, but remains in computer memory so it can be reactivated later. This technique partially overcame DOS's limitation of executing only one program, or task, at a time. TSRs are used only in DOS, not in Windows.
Which still leaves the question what the purpose of loading a TSR in the Windows virtual machine but not in others would be.
> For example, you might install network drivers to support your Windows programs. You might choose this option instead of installing them globally because you don’t care about networking for your MS-DOS programs and want to free up conventional memory for them. Or because those drivers don’t support running in multiple virtual machines, so you’ll take them in the System VM and forego them for your MS-DOS programs.
In the Windows 95 era, it was not uncommon to still rely on MS-DOS TSRs for important functionality. Raymond has explained elsewhere about how Windows, after “sucking the brains out of MS-DOS,” maintained the ability to call into these TSRs.
Since this article doesn't actually define what a TSR is and not everyone has DOS terminology in their resident memory: https://en.wikipedia.org/wiki/Terminate-and-stay-resident_pr...
> A terminate-and-stay-resident program (commonly TSR) is a computer program running under DOS that uses a system call to return control to DOS as though it has finished, but remains in computer memory so it can be reactivated later. This technique partially overcame DOS's limitation of executing only one program, or task, at a time. TSRs are used only in DOS, not in Windows.
Which still leaves the question what the purpose of loading a TSR in the Windows virtual machine but not in others would be.
The blog post answers your question directly:
> For example, you might install network drivers to support your Windows programs. You might choose this option instead of installing them globally because you don’t care about networking for your MS-DOS programs and want to free up conventional memory for them. Or because those drivers don’t support running in multiple virtual machines, so you’ll take them in the System VM and forego them for your MS-DOS programs.
In the Windows 95 era, it was not uncommon to still rely on MS-DOS TSRs for important functionality. Raymond has explained elsewhere about how Windows, after “sucking the brains out of MS-DOS,” maintained the ability to call into these TSRs.
I love Raymond’s periodic peeks into how Windows/386 and later were not just shells atop DOS shells, as they are often derided.