1. The data elements in field 007 are positionally defined and the number of character positions in field 007 depends upon the code contained in 007/00. Character position 00 contains a code that identifies the category of material. The fill character (|) is not allowed in this position. The fill character may be used in any other character position when the cataloging agency makes no attempt to code the position.

The categories of material for which field 007 is applicable in bibliographic records are presented in the following order in the field description: map, electronic resource, globe, tactile material, projected graphic, microform, nonprojected graphic, motion picture, kit, notated music, remote-sensing image, sound recording, text, videorecording, and unspecified.

2. A subnet mask increases the amount of address that is deemed to be "network" thereby reducing the amount of host for each address.

e.g. Class C address 194.64.48.86, mask 255.255.255.240

In binary:

Address 11000010.01000000.00110000.01010110

Mask 11111111.11111111.11111111.11110000

So the network is the 28 most significant bits.

To determine the subnet, the address is ANDed with the mask.

Address 11000010.01000000.00110000.01010110

Mask 11111111.11111111.11111111.11110000

=========================================

ANDed 11000010.01000000.00110000.01010000

Thus, to determine whether two addresses are in the same subnet, the address is ANDed with the mask, and the two results compared.

E.g. Is 194.64.48.86 in the same subnet as 194.64.48.162, when a mask of 255.255.255.240 is applied?

Address 11000010.01000000.00110000.01010110 194.64.48.86

Mask 11111111.11111111.11111111.11110000 255.255.255.240

=======================================================

ANDed 11000010.01000000.00110000.01010000 194.64.48.80

Address 11000010.01000000.00110000.10100010 194.64.48.162

Mask 11111111.11111111.11111111.11110000 255.255.255.240

========================================================

ANDed 11000010.01000000.00110000.10100000 194.64.48.160

Subnets are 194.64.48.80 and 194.64.48.160, so they are not in the same subnet.

Only the last octet need really be considered when testing this - 195.200.21.50 is clearly not the same network!

Also, if the subnet is applied in this way, simply determining the least significant bit of the mask (in our case, 100002 or 16) gives the number of addresses in each subnet, so the addresses will be 0-15, 16-31, 32-47, 48-63, etc. As "all zero" and "all one" addresses are not allowed, 194.64.48.0, 194.64.48.15, 194.64.48.16, 194.64.48.31, 194.64.48.32, etc. are not legitimate when masked to 255.255.255.240 (in binary, these make the last 4 bits all zeroes or all ones; these are the host addresses reserved for network or broadcast).