Well, this is something I got to know from my elder brother. Actually, we have a departmental shop in my hometown. My father started the shop even before my birth and my elder brother also joined him after passing 12th as he did not want to continue his study. One day, I also happened to handle the shop when my father and brother left for another city. The whole day I struggled with the calculator as I didn't know its functionality and took long in calculating figures making the customers wait slightly longer.
However, my brother taught the difference the same night he arrived:
This is what he taught
The C button deletes what you have typed so far while the CE button only deletes your last entry. Something this will happen:
If you press the CE button, you will get this result.
And if you press the C button, this will happen.