CE vs C on a Calculator
TekP says in nutshell CE = Clear Entry while C = Clear as in just clear everything.
According to Vintage Technology, both buttons are a way to clear or cancel an entry. The C button will clear all input to the calculator. The CE button clears the most recent entry, so if you make a mistake in a long computation, you don’t need to start all over again.
https://superuser.com/questions/449637/whats-the-difference-between-c-and-ce-functions-on-windows-calculator