The most common simple hardware to be seen nowadays is the IBM-compatible personal computer (XT, AT, AT386, 486 etc.) which usually functions under the DOS Operating System. The higher level machines (workstations, file servers etc.) are usually based on the Unix operating system. We will concentrate on these two types of configurations for a couple of additional reasons:
As a result of these two features the user is free to buy the basic system from one vendor, the additional units like tape drives etc. from another vendor and get software from yet another source; thereby managing to substantially reduce costs and also very often enhance performance.
In addition, a large number of low-cost software and hardware is available for such configurations since there are many users and a proliferation of small-scale vendors. Indeed, even the operating systems for such configurations can now be obtained for nominal cost.