The number of edges present in the forest generated by the DFS traversal of an undirected graph $G$ with 100 vertices is 40. The number of connected components in $G$ is ________

A DFS traversal on an undirected graph with $n$ vertices and $k$ connected components produces a DFS spanning forest consisting of $k$ trees.

Let the $i$-th connected component have $n_i$ vertices. The DFS tree spanning this component has $n_i - 1$ edges.

The total number of edges $E_F$ in the DFS forest is the sum of edges across all $k$ trees:

Given $n = 100$ and $E_F = 40$:

Therefore, the number of connected components in $G$ is 60.