The VIRMOS mask manufacturing tools: a) mask preparation software

VIMOS and NIRMOS are two multi Object Spectrographs being developed for the VLT. Their main scientific characteristic is the high multiplexing capability, allowing to obtain up to 800 spectra per exposure. To achieve such a high efficiency, a number of dedicated tools are necessary, from software to hardware. In part a), we describe the software tools which will be provided to successful proponents to prepare observations. Paper b) will deal with the technical aspects of mask manufacturing