- In geometry, a cube or regular hexahedron is a three-dimensional solid object bounded by six congruent square faces, a type of polyhedron. It has twelve congruent edges and eight vertices. It is a type of parallelepiped, with pairs of parallel opposite faces, and more specifically a rhombohedron, with congruent edges, and a rectangular cuboid, with right angles between pairs of intersecting faces and pairs of intersecting edges. It is an example of many classes of polyhedra: Platonic solid, regular polyhedron, parallelohedron, zonohedron, and plesiohedron. The dual polyhedron of a cube is the regular octahedron.
- Windows 2.1 (Wikipedia)
It was released with two different variants with differing CPU compatibility, also known as Windows/286 and Windows/386, so the versions are considered to be similar to its predecessor. In comparison, the Windows/386 variant is considered to be better than Windows/286, since it provides support for EMS emulation and is designed to use both conventional and extended memory. Changes to the user interface did not occur in this version, and rather, its performance was increased and enhanced memory management was added. The version is also noted to be the first one to require a hard disk drive. A minor update version, Windows 2.11, was released in March 1989.