Geographic data can be stored in a vector graphics or a raster graphics format. Using a vector format, two-dimensional data is stored in terms of x and y coordinates. A road or a river can be described as a series of x,y coordinate points. Nonlinear features such as town boundaries can be stored as a closed loop of coordinates. The vector model is good for describing well-delineated features. A raster data format expresses data as a continously-changing set of grid cells. The raster model is better for portraying subtle changes such as soil type patterns over an area. Most geographic information systems make use of both kinds of data.

GISs do these kinds of things:

• They accept geographic input in the form of scanned-in and digitized map images. Often this data is supplied by a source that may own maps and has already digitized them.
• They rescale or otherwise manipulate geographic data for different purposes
• They include a database manager, usually a relational database management system (RDBMS).
• They include query and analysis programs so that you can retrieve answers to simple questions such as the distance between two points on a map or more complicated questions that require analysis, such as determining the traffic pattern at a given intersection.
• They provide answers visually, usually as maps or graphs.

• ArcInfo/ArcView Shape
• Mapinfo MIF/MID
• Microstation DGN