Open architecture
IBM was in a hurry and assembled the computer from other companies' components: a processor from Intel and an operating system from a small firm called Microsoft. It also published the technical documentation. Compaq then legally reverse-engineered the BIOS and began selling compatible clones. The market for “PC compatibles” was born.
Who won
Paradoxically not IBM. Microsoft, which kept the rights to DOS, and Intel earned the most. In 2005 IBM sold its PC division to Chinese company Lenovo.
Legacy today
When you build a computer today, you use the x86 architecture and the idea of interchangeable components that began with the IBM PC. See How to build a PC.