Magnetic core memory was the second major milestone in modern computer memory technology that was widely adopted. While it is generally believed that all key components of the technology had been developed by 1951, the idea is traced back to MIT's Jay Forrester who first described the technology in 1949. In parallel An Wang was working on magnetic core memory in a slightly different approach as well. The basic principle of core memory was using a "core" as a ring of ferrite that could be magnetized in one of two directions. As a result, the memory was able to store digital information either a 1 or 0. In the 1960s up to the early 1970s, non-volatile magnetic core memory was used as the default memory technology in more than 90 percent of all computers globally. Wang received the initial patent (#2,708,722) with 34 claims for magnetic core memory, which was acquired shortly after its approval in 1955 by IBM for $500,000. MIT challenged the patent claims and engaged in a lengthy patent battle with IBM. IBM eventually paid MIT $13 million for the rights to magnetic core memory in 1964.