Discuss short and convenient method (bond line notations) of representing organic molecules ?

In these notations, the bonds are represented  by lines and carbon atoms by line ends and intersections. For example. 
(i) n-Hexane may be represented as:



(ii) 2-Methylbuta-1, 3-diene may be represented as:



(iii) Hexa -1, 3, 5-triene may be represented as: