Final answer:
The company that provided IBM with the operating system for its PC was Microsoft, which played a significant role in the personal computing industry and later faced antitrust allegations due to its dominant market position.
Step-by-step explanation:
The software company that provided IBM with the operating system for its PC was c) Microsoft. During the early stages of the personal computer industry, various companies contributed different elements to computing and networks. IBM, a dominant hardware manufacturer, sought to enter the burgeoning PC market and needed an operating system for their new product. Microsoft, founded by Bill Gates and Paul Allen, stepped in to provide this essential software. The partnership between IBM and Microsoft helped to standardize the personal computing industry around Microsoft's operating systems, eventually leading to a widespread proliferation of the MS-DOS and later Windows platforms.
Microsoft's influence grew to such an extent that by the mid-90s, the U.S. government became concerned that the company had a monopoly over computer operating systems. Antitrust regulators accused Microsoft of engaging in anticompetitive practices, such as exclusive dealing and tying its Windows operating system with its Internet Explorer browser, leveraging its dominance to erode competition. These historic legal battles highlighted the balance between innovation, market power, and regulation in the tech industry.