My dad was recently admitted in the hospital, he was talking nonsense and trembling really bad, but he could answer president, year, dob and name.

Stroke: A thalamic stroke can lead to some of these speech problems but hey, i'm a neurologist, so i will point that out. I am sure that doctors in the hospital will also make sure that nothing else is the matter as well, e.g. Infection, heart issue, etc.

Altered Mental Stat: There can be many reasons for an altered mental status, especially in the elderly. It sounds like at least some aspects of his long-term memory are intact. He will need a comprehensive assessment to determine the cause.