Umbriel (moon) that obliterated its older surface. Covered by numerous impact craters reaching in diameter, Umbriel is the second most heavily cratered satellite of Uranus after Oberon. The most prominent surface feature is a ring of bright material on the floor of Wunda crater. This moon, like all moons of Uranus, probably formed from an accretion disk that surrounded the planet just after its formation. The Uranian system has been studied up close only once, by the spacecraft "Voyager 2" in January 1986. It took several images of Umbriel, which allowed mapping of about 40% of the moon’s surface. Umbriel, along with
Oberon (operating system) together with the editor called Write yielded V2. As foreshadowed in the table in section history above there was a major fork in the beginning of 1990s: V4 vs. System 3: The group around Jürg Gutknecht introduced persistent objects and object-libraries thereby extending the kernel. The group around realized similar features by introducing active elements mapped to a special character thereby extending fonts without changing the kernel. System 3 was sometimes also called Spirit of Oberon and later renamed to ETH Oberon, whereas V4 was sometimes also called Linz Oberon. A version of the Oberon System 3, which was integrated