ضَرَبْتُ زَيْدًا — I struck Zayd.
ضَرَبْتُ is a past-tense verb; the attached تُ is a first-person singular pronoun functioning as the subject in the nominative position. زَيْدًا is the direct object, accusative with visible fatḥa. The subject is a visible attached pronoun, not a separate noun.