Which theoretical model of computation accepts or rejects strings of symbols and yields exactly one computation for each input?

• A. Turing Machine
• B. DFA (Deterministic Finite Automaton)
• C. NFA (Nondeterministic Finite Automaton)
• D. Pushdown Automaton

Answer: (B)

The essential idea is determinism: a model that processes a string in which there is exactly one way to proceed at every step. In a deterministic finite automaton, the transition function is defined so that for every current state and input symbol, there is exactly one next state. This makes the whole run on any input string unique—a single computation path. After consuming the entire input, the machine halts in either an accepting state (string is accepted) or a non-accepting state (string is rejected).

This fits the description because it guarantees exactly one computation for each input, which is the hallmark of determinism in this context. The other models either allow branching paths (nondeterminism) or use extra structure (like a stack in a pushdown automaton or the general, more powerful capabilities of a Turing machine), which means they do not inherently restrict to a single computation path for every input.