IUPAC Naming of Bicyclo compounds:

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Bicyclic molecules are described by IUPAC nomenclature. The root of the compound name depends on the total number of atoms in all directly connected rings together, possibly followed by a suffix denoting the functional group with the highest priority.
Bicyclio compounds are characterised by bridgehead atom.The atoms where the ring met are called bridgehead atoms.
Numbering of the carbon chain always begins at one bridgehead atom and follows the carbon chain along the longest path, to the next bridgehead atom. Then numbering is continued along the second longest path and so on.
Fused and bridged bicyclic compounds get the prefix bicyclo.
In between the prefix and the suffix, a pair of brackets with numerals denotes the number of carbon atoms between each of the bridgehead atoms. These numbers are arranged in descending order and are separated by periods.

Example 1:Norbornane

Example 1: The carbon frame of norbornane contains a total of 7 atoms, hence the root name heptane. This molecule has two paths of 2 carbon atoms and a third path of 1 carbon atom between the two bridgehead carbons, so the brackets are filled in descending order: [2.2.1].
Addition of the prefix bicyclo gives the total name bicyclo[2.2.1]heptane.

Example 2: Camphor

Example 2 : The carbon frame of camphor also counts 7 atoms, but is substituted with a carbonyl in this case, hence the suffix heptanone.We start with numbering the carbon frame at the bridgehead atom with the highest priority , hence the bridgehead carbon in front gets number 1, the carbonyl gets number 2 and numbering continues along the carbon chain following the longest path, until the doubly substituted top carbon (number 7).
Equal to norbornane, this molecule also has two paths of 2 carbon atoms and one path of 1 carbon atom between the two bridgehead carbons, so the numbers within the brackets stay [2.2.1].
Combining the brackets and suffix (now filling in the position of the carbonyl as well) gives us [2.2.1]heptan-2-one. Besides bicyclo, the prefix should also specify the positions of all methyl substituents so the complete, official name becomes 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one.

Example 3: Decalin

When naming simple fused bicyclic compounds, the same method as for bridged bicyclic compounds is applied, except the third path between the two bridgehead atoms now consists of zero atoms.
Therefore, fused bicyclic compounds have a "0" included in the brackets.
Example: decalin is named bicyclo[4.4.0]decane.

Example 4:Bicyclobutane.

The numbers are sometimes omitted in unambiguous cases.
Example: bicyclo[1.1.0]butane is typically called simply bicyclobutane.

Example 5:DABCO

Naming of heterobicyclic compounds: The heterocyclic molecule DABCO has a total of 8 atoms in its bridged structure, hence the root name octane.
Here the two bridgehead atoms are nitrogen instead of carbon atoms. Therefore, the official name gets the additional prefix 1,4-diaza and the total name becomes 1,4-diazabicyclo[2.2.2]octane.

Example 6:Norbornadiene

Skeleton similar to Norbornane exept the two pi bonds at carbon no 2 and 5. It is named as Bicyclo (2.2.1)hepta-2,5-diene.