MIDAS has benefitted greatly from the experience gained at ESO using the Hewlett-Packard based image processing system IHAP (see F. Middelburg, IHAP Manual, ESO 1985). Not only have many of the internal design features such as ``world coordinates'' been incorporated, but also the command language has been designed in such a way that it is similar to the basic philosophy of IHAP.
The MIDAS system can be run in both an interactive and a batch mode. In addition, the interactive user will be able to create batch jobs which will run in parallel with the interactive work.
MIDAS is based on three sets of general interfaces for application programs to data structures, namely: a) the ``Standard Interfaces'' for general I/O and image access, b) the ``Table Interfaces'' for access to table structures, and the ``Graphics Interfaces'' for data representation in graphical format. These interfaces allow easy integration of application programs into MIDAS. To provide a portable system a layer of OS-routines have been used to shield MIDAS from the local operating system. These routines may only be used at lowest levels and are not available for normal applications.
To facilitate easy implementation of different graphic and display devices, MIDAS has adopted a set of device independent interfaces for plotting and image display. All plotting routines in MIDAS are based on the ASTRONET Graphic Library, developed and maintained by the italian ASTRONET. Further, the image display applications are using the Image Display Interface routines defined in collaboration with ST ScI, UK STARLINK, KPNO and Trieste Observatory.