I mean, can u give me the alogarithm of addition n multiply of matrix, that user can give input size of matrix n user can create some matrix.

That matrix can be saved in memory n suddenly it can be accsess...

Well, creation of the algorithm is pretty easy - you have two steps, so you're either going to have two functions (one for add, one for multiply), or you are going to do them sequentially. So knowing this, you can then write down the steps to fully add or multiply a matrix. (I'm not sure what the exact method is for each, but i'm sure you could Google "matrix addition" or "matrix multiplication" and figure them out pretty easily. From there, just make it into pseudocode (try to implement a loop or function for the parts that are repeated), and you have it.

If you come back with code or specific questions we can try to help you more, but we cannot just "give you" the answers. That should get you started anyway.