# Introduction

GILDAS is one of the numerous image processing systems used in Astronomy. GILDAS was born sometime ago in the Groupe d'Astrophysique de Grenoble (now LAOG, Laboratoire d'Astronomie de l'Observatoire de Grenoble), and has been adopted as the IRAM standard data reduction package. GILDAS is jointly maintained by IRAM & LAB (Laboratoire d'Astrophysique de Bordeaux). GILDAS contains many facilities, most of which are oriented towards spectral line mapping, or in fact all kind of 3-dimensional data.

GILDAS has grown on top of two pre-existing programs, CLASS and GREG, which seemed to please their users. As many other packages, GILDAS had to move out of its original VAX-VMS environment towards the growing Unix area. The original software was modified in order to run on VMS and Unix operating systems, with (near) transparent file sharing even between heterogeneous computers. The current implementation even allows remote task submission on a compute server from a workstation. VMS is no longer supported, but a Windows version is available and supported.

This guide is a general introduction to the GILDAS package. It does not describe any utility, but gives cross-reference to other documentations and many usefull hints on how to customize your GILDAS environment.