Here some calculators which I have written in C and Python.
These were written to help in achieving some objective. For example, the prime number codes were written to help in solving a problem there on Project Euler. IDFT and DFT calculators were written to check the answers to certain questions in digital signal processing that I have computed myself.
Some codes have been marked as 'Not Perfect". This is mainly because they compute the right answer (as per the books) and sometimes they compute answers in which some starting elements are wrong. This problem is mainly with the codes I had written for calculating DFT, IDFT and circular convolution. Well what can I say? The way this subject was taught!! Nobody in the whole class knows how to practically implement a filter but everyone knows how to compute DFT by hand.