I believe my mid-80s TI (bought for O levels) still works, and that would be my preferred calculator in absence of an interactive programming language. It got me through most of my exams (it lacked hyperbolics, which I needed for the MSc, but my back-up calculator provided those), bar the DipCompSci—the CU-approval regulations came in before that but after my Part II and it was too primitive (see above) to be allowed. Sadly, no calculations were required for that last set of papers, otherwise I would have been gleefully reaching for the log tables.