First of all, we need to distinguish between the name of a node or the name of an edge and their internal numbers . The name can be any string. Its is saved in the graph file (see 2.2). The internal number is generated automatically when loading a graph. The nodes and the edges have consecutive internal numbers starting from 1. When using the Scilab functions working on graphs, all the computations are made with internal numbers.
It is very important to give different names to the nodes because the nodes are distinguished by their names when they are loaded. This distinction is not important for edges.
Often, the names are taken as the internal numbers. This is the default when no names are given. In this case, the distinction between a name and a number is not meaningful. Only the type of the variable is not the same: the name is a string and the number is an integer.
In the following when we talk about the number of a node or the number of an edge, we mean the internal number.