The number of subgroups, normal subgroups and characteristic subgroups of a finite group G are denoted by Sub(G), NSub(G) and CSub(G), respectively. The main goal of this paper is to present a matrix model for computing these positive integers for dicyclic groups, semi-dihedral groups, and three sequences U6n, V8n and H(n) of groups that can be presented as follows: U6n = ⟨ a, b | a2n = b3 = e, bab = a⟩ , V8n = ⟨ a, b | a2n = b4 = e, aba = b− 1, ab− 1a = b⟩ , H(n) = ⟨ a, b, c | a2n− 2 = b2 = c2 = e, [a, b] = [b, c] = e, ac = ab⟩ . For each group, a matrix model containing all information is given.