sentences:  This is exploited by thread libraries to provide cooperative multitasking facilities without using codice_64 or other fiber facilities.Whereas codice_64 is a library service which can create an execution context in heap-allocated memory and can support other services such as buffer overflow protection, abuse of codice_1 is implemented by the programmer, who may reserve memory on the stack and fail to notify the library or operating system of the new operating context.On the other hand, a library's implementation of codice_64 may internally use codice_1 in a fashion similar to this example to save and restore a context, after it has been initialised somehow.