4 The top level of hierarchy is a vendor list.
5 Each vendor has a 2-byte long id, stored in database as 4 hexadecimal digits (with lowercase letters).
6 They can be browsed <a href='/read/PC'>here</a>.
10 Each vendor contains a list of its devices.
11 Each device in the list has a 2-byte long id, stored the same way as vendor id (4 hexadecimal letters).
14 A device can consist of more sub-systems.
15 Each sub-system has 4-byte long id, stored as 8 hexadecimal letters, split in the middle by a space (for example <tt>1234 abcd</tt> could be a sub-system id).
16 The first quad of digits is considered a vendor id (from the same list of vendors). The vendor of the sub-system can be different than vendor of the device.
20 You can have a look at <a href='$HELP_URL$pci_class'>PCI device classes</a>.