Q: Why won't the Rainbow run my favorite IBM PC programs?
The Rainbow is not IBM compatible. The Rainbow was designed to be an MS-DOS compatible machine, not an IBM compatible machine. Most people do not understand the difference. IBMs do run MS-DOS programs, but they mostly run IBM compatible programs. When the Rainbow was introduced, many felt that, like CP/M, MS-DOS programs would run on any hardware, as long as the hardware also ran MS-DOS. At first, this seemed to be the case, but, as years passed, less and less programs made were MS-DOS compatible, while more and more were IBM compatible.
The reason for this incompatibility was that most programs being written directly accessed the IBM PCs hardware and did not operate through the operating system. Programs that do very little direct hardware access on the IBM PC might run on the Rainbow. See the Software compatibility section for more information.