sentences:  This freed up the equivalent amount of critical "base" or conventional memory, the first 640 KB of the PC's RAM – the area in which all DOS applications run.Additionally, on Intel 80386 machines, DR DOS's EMS memory manager allowed the operating system to load DOS device drivers into upper memory blocks, further freeing base memory.DR DOS 5.0 was the first DOS to integrate such functionality into the base OS (loading device drivers into upper memory blocks was already possible using third-party software like QEMM).