Introduction

The program described here is a general code for modelling interstellar or intergalactic absorption features on an initial polynomial continuum which may also contain emission lines. For each absorption line the input parameters are : atomic transition, column density, thermal width and position (velocity shift).

The output spectrum is computed at a given instrumental resolution and can therefore be used for a direct comparison with observations (provided that the lines are resolved). In this case the step is completely interactive with no possibility for a ``least square approach''.