If you enjoy maths, I suggest creating an RPN (Reverse Polish Notation) calculator. The concept is fairly easy to understand and use. The difficult part is implementation of the concept obviously. There are a few online RPN calculators, some of which are simple while others are complex.
Here are a couple of RPN calculators:
- Hewlett-Packard makes RPN calculators for sale. This is a simple online version.
- contains information below the calculator
- 2 different calculators, the last more complex than the first (RPN calc 2 is simply wrong with multiple computations)
References (external links from the following page, which also has information):
2 + 3 * 4 would be calculated using
3 [ENTER] 4 * 2 +
2 [ENTER] 3 [ENTER] 4 * +
How about something more interesting like this:
(2 + 3) * 4 ?
4 [ENTER] 2 [ENTER] 3 + *
2 [ENTER] 3 + 4 *
It can be a really good challenge to program, whether it is for a hobby or for a college project or even for a job (Hewlett-Packard actually makes RPN calculators for sale). If you choose this, I wish you good luck!