Mathca is desktop software for performing and documenting engineering and scientific calculations. First introduced in 1986 on MS-DOS, it was the first to introduce live editing of typeset mathematical notation, combined with its automatic computation. It was also the first to automatically compute and check consistency of engineering units such as the International System of Units (SI). Mathcad today includes some of the capabilities of a computer algebra system but remains oriented towards ease of use and numerical engineering applications. Mathcad was conceived and originally written by Allen Razdow (of MIT), co-founder of Mathsoft which is now part of Parametric Technology Corporation.