An Example of Virtual Storage using Paging

Suppose we have a computer with 20 pages of 512 bytes each, and also
suppose that the user is requesting a maximum of 30 pages.  Some of
the pages will be in RAM and some will not.  In the following table
pages 0,1,2,3,8,9,10, and 12 have been loaded.  The rest are on the
hard drive.  


Virtual    i  Page          Physical    Starting
Page       c  Table         Memory      Address
Number     b                 Page

00  ------ 1   11             00              0
01  ------ 1   16             01            512
02  ------ 1    3  ----|      02           1024
03  ------ 1    5  -|  |---   03           1536
04         0        |         04           2048
05         0        |------   05           2560
06         0                  06           3072
07         0        |------   07           3584
08  ------ 1    1   |         08           4096
09  ------ 1    7  -|         09           4608
10  ------ 1   14             10           5120
11         0                  11           5632
12  ------ 1    6             12           6144
13         0                  13           6656
14         0                  14           7168
15         0                  15           7680
16         0                  16           8192
17         0                  17           8704
18         0                  18           9216
19         0                  19           9728
20         0
21         0
22         0
23         0
24         0
25         0
26         0
27         0
28         0
29         0




Virtual Address       Virtual    Offset      Physical     Starting    Real
7 bits    9 bits         Page                  Page        Address   Address
                                                           of Page   of byte

1032d
0000010 000001000          2       8             3          1536     1544

4111d
0001000 000001111          8       15            1           512      527

4607d
0001000 111111111          8      511            1           512     1023

4608d
0001001 000000000          9        0            7          3584     3584

0000100 000000001          4        1            --


      bit         value
      position

      1             1
      2             2
      3             4
      4             8
      5            16
      6            32
      7            64
      8           128
      9           256
      10          512
      11         1024
      12         2048
      13         4096
      14         8192
      15        16384
      16        32768