And the LED ones had relatively short battery life; they were rechargeable. When I started college, HP calculators were still very expensive so I started with a TI. Within a year or two, you could get an HP LED model (HP-55 in my case) for a reasonable price. Through college I still took a slide rule to exams as a backup in case the battery died for some reason though I never had to use it. During the latter part of the 70s, calculators were dropping in price extremely rapidly.
