Introduction

In order to provide a device-independent graphics package, the Italian Astronet Graphic Library has been adopted as the standard low level library for the plot package in MIDAS. One of the main reasons for using the AGL package rather than one of the more evolved and sophisticated packages (e.g. GKS) was the fact that the AGL   package is simple; meanwhile AGL is still capable of doing the things one needs for reasonably advanced graphics, in particular with respect to interactive facilities. The AGL graphics library is fully integrated within the MIDAS directory structure and is generated like every other MIDAS subroutine library during installation. For an extensive description of the package we refer to the AGL User's and Installation Guides for Version 3.

The graphic facilities available in MIDAS can be divided into three main categories of commands, based on their functionality:

• general plot commands   that deal with the setup of graphic packages: the assignment of the graphics device, routing a plot file to a graphic device, and general (over)plot commands for text, line, symbols, etc.;
• main plot commands   which do the actual plotting and overplotting of data (i.e. images, tables, descriptors or keywords);
• cursor commands   which use the graphics cursor.

Below, subsection 6.1.2 first describes how graphic display units (e.g. terminals, workstations) can be activated inside the MIDAS environment. Thereafter, in the subsections  6.1.3 to 6.1.5 the plot commands available in MIDAS will be discussed. In subsection 6.1.6 information can be found about how plot files can be manipulated. In section 6.1.8 a number of examples are presented to illustrate the available commands and their syntax. Finally, in subsection 6.1.9 an overview is given of all the available graphic commands in MIDAS.