An algorithm is an abstract description of how to solve a problem. Algorithms are not specific to any programming language. There is no particular structure to algorithms: they can be written in any way understandable to someone else.
A "MATLAB algorithm", to the extent those can be said to exist at all, would be an outline of how to solve a problem using the facilities of MATLAB.
"Is it the accumulation of codes for writing any program?"
No. An algorithm is not code, it is any formal method of doing something. If you tell someone "Take the milk out of the refrigerator and look behind it and get the jar of jam there", then that is an algorithm for getting jars of jam out.
