Final answer:
Mainframe computers are usually compatible with the IBM System/360 line introduced in 1965, unlike minicomputers, microcomputers, or supercomputers.
Step-by-step explanation:
The IBM System/360, introduced in 1965, was a line of mainframe computers, which means that the compatible computers are likely to be mainframes as well. Minicomputers, introduced in the 1970s by companies like Digital Equipment Corporation and others, were indeed smaller and less expensive than mainframes, but they were not directly compatible with the IBM System/360. In contrast, microcomputers and supercomputers represent different classes of computing power and purposes and do not match the compatibility with the IBM System/360 mainstream mainframe computers of that era.