Shape::TRIANGLE, 8 or Color::RED aren't concepts. They're merely symbols. In principle, you will find them encoded in some way under a microscope (as some arrangement of physical states, though it will depend on the particular physical medium what the particular arrangement will look like). Your computer program can process that physical state to mimic some aspects of reasoning, but that's entirely a matter of how the program is designed to operate with these physical arrangements. You cannot analyze or derive anything from the symbols qua symbols themselves because there's no meaning there to analyze or from which to derive things.
In this context, these symbols are conventional signs taken to refer to meanings that are not themselves. Concepts are apprehensions of form, or we might say "meanings", the what-it-is-to-be of the given thing. When I write "123", that series of characters obviously is not itself the number 123. A human interpreter in possession of a mental dictionary can read that series of squiggles to arrive mentally at the concept of the number 123. But all that exists in computers are representations, not the things they are meant to represent, and their meanings are entirely in the mind of the human observer who assigns conventional meanings to those representations.
How is that different from our brains? All that exists in us may very well be our neuronal representations of a concept. Alternatively, the meaning of a representation in a computer is interpreted and acted upon by other elements within a computer
