On the 12th of August 1981 the first ever personal computer - the IBM 5150 - was announced. It became one of the most important releases in the world of technology, ever.
With a fraction of the power of today's machines, the 5150 stood proud with an Intel 8088 processor running at an almighty 4.77MhZ, 16kB (max 640kB) of memory and loaded with IBM Basic/MS DOS 1.0. Despite not coining the common acronym "PC", the 5150 defined it as being the standard which complied with IBM's specifications.
IBM created the 5150 with an "open architecture" which meant other manufacturers could create machines, after buying a licence for the BIOS from IBM. Other manufacturers weren't content with paying IBM, so circumvented this licence charge by reverse engineering the BIOS.
The BBC has produced an article about the 5150, the last 25 years of IBM computing and what the future holds for the IBM PC.