The  Software  for   a geographical  information system may be split into five functional groups :
 
 

• Data Input and Verification
• Data storage and database management
• Data output and presentation
• Data transformation
• User interface

Data Input and verification :
 

This functional part covers all aspects of capturing spatial data from the existing maps, field observations, and sensors and converting them  to a digital form
 

Data storage and database management :
 

It handles the way in which data about location, topology ( linkage ), and attributes of geographical elements - points, lines, area and surface - are  structured and organized, both with respect to the way they must be handled in the computer and how they are perceived by the users of the system.
 

Data output  and presentation :
 

This unit is concerned with the ways the data are displayed and how the results of analyses are reported to the users in the form of maps, tables and figures etc.
 

Data transformation :
 

It embraces two classes of operation - a)  transformation needed to removed errors from the data or to bring them up to date or to match them to other data sets. and b) the large array of analysis methods that may be applied to the data in order to achieve the answers to questions asked of the GIS  e.g. Where are all  the  five-star hotels located ? Which are the major tourist centers from this  hotels ? etc. Many of these transformtions can operate on the spatial, topological and the non-spatial ( attributes ) aspects of the data, either separately or in combination.
 

User Interface:
 

As the requirements of GIS users to retrieve and transform data are unlimited, the system must provide a range of interfaces by which they can interact with the system. Menu-driven interface  or command line interpretor or combination of both  can be provided.