In programming, a data structure consisting of zero or more nodes and zero or more edges, which connect pairs of nodes. If any two nodes in a graph can be connected by a path along edges, the graph is said to be connected. A subgraph is a subset of the nodes and edges within a graph. A graph is directed (a digraph) if each edge links two nodes together only in one direction. Graphical Device Interface graphics import component graph is weighted if each edge has some value associated with it.