NFA for strings starting with a or bb

This epsilon-NFA illustrates a language with alternative prefixes. It reads the first symbol at q0. An a moves to qa, while a b moves to q1, which needs a second b to reach qb. The two successful branches then merge into qf by epsilon, where the machine can consume any remaining symbols. The epsilon transitions mean the required prefix itself is enough for acceptance; no extra input is needed before qf. The drawing shows that acceptance depends on the beginning of the input rather than its end. Prefix languages are common in token recognition, command parsing and protocol dispatch, where the first few symbols choose a valid form.