Maintaining a graph in memory by means of its adjacency matrix is known as:

Correct answer: Sequential Representation

Explanation: An adjacency matrix represents a graph as an n × n two-dimensional array where the entry at row i and column j indicates whether an edge exists between vertex i and vertex j (or stores the weight of that edge). This storage is array-based, so it is called a sequential representation.

• Storage: uses a 2D array of size n × n, so memory is O(n²).

• Edge lookup: checking existence of an edge between two vertices is O(1) by indexing into the matrix.

• Best use case: efficient for dense graphs where many edges exist.

• Alternative: a linked (adjacency list) representation stores a list of neighbors per vertex and is more memory-efficient for sparse graphs.

Summary: Maintaining a graph by its adjacency matrix is called the sequential (array-based) representation because the graph is stored in a contiguous two-dimensional array.