and 1 of memory are occupied by another process and thus unavailable). This is
an example of a page fault, because the desired page of the program had to be
fetched from disk. When address 1 is referenced, the data already exists in memory
(so we have a page hit). When address 2 is referenced, this causes another
page fault, and page 1 of the program is copied to frame 0 in memory. This continues,
and after these addresses are referenced and pages are copied from disk to
main memory, the state of the system is as shown in Figure 6.15a. We see that
address 0 of the program, which contains the data value “A”, currently resides in