an ordered list of points. A polygon, representing a region of space, defined by its boundary, a polyline with coincident starting and ending vertices. A variety of more complex shapes may be supported: Parametric curves, in which polylines or polygons are augmented with parameters to define a non-linear interpolation between vertices, including circular arcs, cubic splines, Catmull–Rom splines, Bézier curves and bezigons. Standard parametric shapes in two or three dimensions, such as circles, ellipses, squares, superellipses, spheres, tetrahedrons, superellipsoids, etc. Irregular three-dimensional surfaces and solids, usually defined as a connected set of polygons (e.g., a polygon mesh) or as parametric surfaces (e.g., NURBS). Fractals, often defined as an iterated function system. In many vector datasets, each shape can be combined with a set of properties. The most common are visual characteristics, such as color, line weight, or dash pattern. In systems in which shapes represent real-world features, such as GIS and BIM, a variety of attributes of each represented feature can be stored, such as name, age, size, and so on. In some Vector data, especially in GIS, information about topological relationships between objects may be represented in the data model, such as tracking the connections between road segments in a transport network. If a dataset stored in one vector file format is converted to another file format that supports all the primitive objects used in that particular image, then the conversion can be lossless. Vector display hardware Vector-based devices, such as the vector CRT and the pen plotter, directly control a drawing mechanism to produce geometric shapes. Since vector display devices can define a line by dealing with just two points (that is, the coordinates of each end of the line), the device can reduce the total amount of data it must deal with by organizing the image in terms of pairs of points. Vector graphic displays were first used in 1958 by the US SAGE air defense system. Vector graphics systems were retired from the U.S. en route air traffic control in 1999. Vector graphics were also used on the TX-2 at the MIT Lincoln Laboratory by computer graphics pioneer Ivan Sutherland to run his program Sketchpad in 1963. Subsequent vector graphics systems, most of which iterated through dynamically modifiable stored lists of drawing instructions, include the IBM 2250, Imlac PDS-1, and DEC GT40. There was a video game console that used vector graphics called Vectrex as well