Way back in the computer Pleistocene era (that is, about ten years ago), PCs were unimpressive creatures, to be sure. Their capacity was limited, their processing was slow, and their interface was all text. Nevertheless, they were great at tasks that were difficult, time-consuming, and boring for humans. In most businesses, PCs rapidly took over the data manipulation, calculation, and word-processing chores that people hated doing. And the more the
PC could do, the more was demanded of it. Hardware and software both had to improve rapidly to meet that demand.
In those early and dark ages, the PC's basic operating system was some version of
DOS (Disk Operating System). Like all other operating systems,
DOS is software that acts as an internal traffic cop—allotting memory, disk space, and central processing unit (
CPU) time to applications, networking software, or peripheral (add-on) equipment. The operating system also keeps track of your files and does all the other behind-the-scenes chores necessary to keep a complicated piece of machinery running.
DOS had weaknesses, including a very limited memory space and a remarkable single-mindedness: Only one small application could run at a time. An early attempt to make the
PC friendlier was Microsoft Windows. The less said about the early versions, the better, but Microsoft stuck with it. Windows 3.1 actually worked—most of the time—though at heart, it was still just a dressed-up version of
DOS. Windows 95, Windows 98, and Windows Me were additional steps toward transcending
DOS restrictions.
Right about the time of Windows 3.1, Microsoft embarked on a parallel path to develop an operating system suitable for the more demanding corporate environment: Windows NT. The first version of NT (version 3.1) was also pretty feeble. Few businesses adopted Windows NT until version 3.5, and Windows NT 4 was the first version to be adopted in large numbers for corporate networks.
Microsoft's operating-system efforts have proceeded along two parallel tracks, because each Windows series is built on a different base of computer code. The tracks can work together and communicate with each other, but their basic kernels are not the same.