A page error is an interrupt that occurs when the software attempts to read or write to a virtual memory location marked as not present. Page errors record the number of times a process must recover from the hard disk. In task manager, page errors are the number of times in a process that data must be retrieved from disk when it is not in memory. Page error values are accumulated from the time the process started. First, the operating system will check the internal table of this process to determine whether it is a valid memory access. If not, terminate the process. If the effective operating system will take out or exchange a free frame in the free frame list, after a disk operation, read the interrupted page back into the newly allocated frame, restart the process, and then the page can be recovered.