Complex sentence: It runs as a graphical, 16-bit multi-tasking shell on top of an existing MS-DOS installation, providing an environment which can run graphical programs designed for Windows, as well as existing MS-DOS software.
Split into simpler sentences: It runs as a graphical, 16-bit multi-tasking shell on top of an existing MS-DOS installation. It provides an environment which can run graphical programs designed for Windows, as well as existing MS-DOS software.