ArcGIS is the most recent GIS software package developed by the Environmental Systems Research Institute (ESRI). ArcGIS represents ESRI's first attempt at merging their two most popular software packages, ArcView and ArcInfo, into a single scalable GIS software environment. Users familiar with the GUI tools first presented in ArcInfo 8.0, the ArcCatalog, ArcMap, and ArcToolbox, will be familiar with the general ArcGIS interface. ArcInfo 9 represents the complete ArcGIS package, ArcEditor 9 is a scaled down version of ArcGIS which includes all of the editing tools of ArcInfo 9, but lacks some of its tools. ArcView 9 is similar to ArcEditor, but provides only tools for editing Shapefiles and personal geodatabases (not ArcInfo coverages and multi-user Geodatabases). Finally, ArcGIS represents a break with ArcView's AVENUE language and ArcInfo's Arc Macro Language (AML). ArcGIS 9 is available only for Windows NT/2000/XP and customizations and programming may be done using Visual Basic, Visual Basic for Applicaitons, and Visual C++.
ArcView is a Desktop Mapping/GIS package developed by the Environmental Systems Research Institute (ESRI). It is a popular package because of its easy to use GUI interface. Initially developed to provide a quick and easy way to display, query through, and navigate around vector based spatial data-sets. ArcView's functionality has increased dramatically by he introduction of add-on "Extensions". For those who are more programming oriented, ArcView also has a script interface which can be used to run program written in AVENUE, ArcView's object oriented programming language. Currently ArcView 3.3 is the default version available in AFS.
Also developed by ESRI, ArcInfo is marketed as a Professional GIS. Traditionally ArcInfo was command line driven, but version 8.0 introduced several GUI items for the NT version which appears to be the focus of current and future ESRI develpment efforts. ArcInfo is generally more robust and powerful than ArcView, allowing greater ability to manipulate processes, and having been built to more easily deal with large data sets. The trdiitonal programming language was Arc Macro Language (AML), but the recent introduction of the Open Development Environment(ODE) provides programming tools for a greater array of programming environments. Currently ArcInfo 9 is the default version available in AFS.
Imagine is a Remote Sensing/Image processing package developed by ERDAS. Traditionally oriented towards manipulation of satellite imagery, Imagine has expanded to accomodate basic photogrammetric needs as well as moving more towards providing "Geographic Visualization". Most interactions with Imagine are done through a GUI, but it does offer a programming interface using Erdas Macro Language (EML). Currently Imagine 8.6 is the default version available in AFS.
"GRASS GIS (Geographic Resources Analysis Support System) is a Geographical Information System (GIS) with raster, topological vector, image processing, and graphics production functionality that operates in the UNIX environment through a graphical user interface and shell in X-Windows. It is released under GNU GPL." (from the GRASS Website). GRASS is command line driven, though the most recent version offers a TCL/TK GUI. Currently GRASS 5.0 is the defalt version in AFS.