SKEDSOFT

Digraph : A digraph D consists of a finite set V of points and a collection of ordered pairs of distinct points. Any such pair (u, v) is called an arc or directed line and will usually be denoted uv. The arc uv goes from u to v and is incident with u and v. We say that u is adjacent to v and v is adjacent from u.

In otherwords, A directed graph or a digraph G consists of a set of vertices V = {v1, v2, .....}, a set of edge E = {e1, e2, .....} and a mapping ψ that maps every edge onto some ordered pair of vertices (vi, vj).

For example, Fig. 8.1(a) below shows a digraph with five vertices and ten edges.