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    <p>How an OS reclaims process resources can (and generally does) vary by OS. On the Windows side of things, the NT-derived OSes behave similarly, so there should be little difference between win XP and win7. Note that asking about 'memory' is an over-simplification in this context, because there are different types of memory. For example, a typical Windows application will have stack memory, heap memory (sometimes multiple heaps), instruction/static memory, and perhaps shared memory. Most of this memory is solely owned by the process, and Windows will reclaim it on process termination (even abnormal termination).</p> <p>However, shared memory can (and often does) have multiple owners; it is tied to a <a href="https://stackoverflow.com/questions/902967/what-is-a-windows-handle">Windows handle</a> (a kernel-level object that can potentially be referenced from multiple processes). Handles have a reference count, and the associated resource is reclaimed if the reference count goes to zero. This means that shared memory can outlive a process that references it. Also, it is possible for a process to 'leak' a handle, and for the handle to never be reclaimed. It is the programmer's responsibility to make sure such handles are properly closed and don't leak; the possibility of abnormal termination complicates this responsibility.</p> <p>On a side note, when Windows 'reclaims' memory, it simply means that memory is available for future allocations to other processes, etc. The actual 1s and 0s are usually going to sit there up until the OS allocates the memory <em>and</em> the new owner of the memory actively over-writes it. So 'reclaiming' doesn't mean the memory is immediately zeroed out or anything like that; scrubbing the memory in this matter is inefficient and often unnecessary. If you are asking out of security concerns, you shouldn't rely on the OS; you'll need to scrub the memory yourself before your process releases it back to the OS.</p> <p>If you want to know more about how modern Windows OSes handle memory, and don't mind doing some digging, the Windows API documentation on MSDN has a lot of information on the subject, but it is a little bit scattered. Good places to start would probably be Windows Handles, and load/unload library/process calls. <a href="http://rads.stackoverflow.com/amzn/click/1572319968" rel="nofollow noreferrer">Application Programming for Windows (Richter)</a> probably has some decent information on this, if I remember right, but I don't have a copy on hand right now to check.</p> <p>Hopefully, someone more knowledgeable about Linux internals can address that side of the question. This is OS-specific stuff, so there are likely to be differences. It might be worth noting that pre-NT Windows (e.g. Windows 95,98,etc.) had a completely different model of process memory. Those differences tended to make it harder for the OS to reclaim memory in the case of abnormal termination; some users found a need to restart the OS frequently if they were running unstable applications, in order to clean up the accumulated memory leak.</p>
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    1. POwhen does an operating system wipes out memory of a process
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    1. COIt seems to me I recall mention of the Windows "idle process" going about and zero-ing memory in its spare time. But in general you are correct.
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    2. CO@BrianWhite I believe you are correct. I recall reading about something like that as well, but years ago, and probably in the context of Windows 2000? I don't know whether they continued to do this in later versions. Sadly, I haven't had much luck googling for it. Anyone have any reference links on this?
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    3. COI wonder if they still do, too. I think Windows has a call to fetch zero'd memory which is why it would be useful to do that while the system is idle. Of course, doing so will wipe out the CPU's data cache and so cause a performance hit to processes that try for low latency when responding to requests.
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