operating system Software for MS-DOS or MicrosoftWindows which originally ran on the 16-bit Intel 8088 and

80286 microprocessors. These used a segmented addressspace to extend the range of addresses from what is possible

with just a 16-bit address. Programs with more than 64

kilobytes of code or data therefore had to waste time

switching between segments. Furthermore, programming with

segments is more involved than programming in a flat addressspace, giving rise to warts like memory models in C and

C++.