You can call your C code in MATLAB in two ways
- Using C MEX API
- Using loadlibrary function
MATLAB Engine API is used to call a MATLAB function (like FFT, that will not be easy to write directly in C) from your C code.
C MEX is similar to C, but not exactly C. You have some predefined function and data APIs that you can use to write your code.
For example, you have mexFunction (which has predefined signature) in MATLAB instead of main in C, mexPrintf in MATLAB instead of printf, mwSize and mwIndex instead of int. C MEX uses mxArray datatype for input and output, you have to first extract that data from mxArray to manipulate them. For that, there are C Matrix APIs. You first write your code in C MEX and then use them after compiling using mex command.
Using loadlibrary, you can load functions from a shared C library (which is purely in C).