Segmentation, Page Fault, and Access Violation
A segmentation fault occurs when a program attempts to access a memory location that it is not allowed to access, or attempts to access a memory location in a way that is not allowed (for example, attempting to write to a read-only location, or to overwrite part of the operating system).
Segmentation is a historic term for the approach to memory management nowadays known as paging (see e.g. Lions' Commentary on UNIX 6th Edition, with Source Code), but the term is still used in the context of "segmentation fault".
On Unix-like operating systems, a signal called SIGSEGV is sent to a process that accesses an invalid memory address. On Microsoft Windows, a process that accesses invalid memory receives the STATUS_ACCESS_VIOLATION exception.
Read more about this topic: Segmentation Fault
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