The SPEFO is written in Borland Turbo Pascal using its graphic library BGI and it consists of an 75 KB long spefo.exe and 245 KB overlay spefo.ovr binary. The program is modular with each module solving particular problem (described in the main menu). Each partial step of processing is secured in a file with characteristic extension, and at the same time the current state of processing is saved in the file's header (e.g. the spectrum after establishing its continuum spline remembers the control points of the polynomial).
Several files must be prepared by hand (in ASCII) before the measurements, to describe the particular type of investigation dependent on the object, personal preferences etc. To this category belongs the list of comparison spectrum lines, the stellar lines under investigation, telluric lines, interstellar ones etc. The result of the processing of particular problem is the comprehensive report file (examples are given below) as well as the graphic plot of the spectra in HPGL format that may be converted to e.g. PostScript and used in publications.
Every action has its prompt and the user is informed each time of what is being done. The data are shown in interactive graphics with possibility of X,Y zooming, panning, setting of control points (the data are recalculated in real time -- so e.g. you can estimate the continuum spline like the rubber band just by inserting and deleting its control points). A very nice part of the SPEFO is the line position measurement in a manner similar to an oscilloscopic comparator. The enlarged spectral line is shown together with its mirrored profile (in another colour) that can be interactively shifted until they match. It is valuable for blended lines for fitting each component, or for asymmetric lines to fit both the wings and the core separately. The more detailed description of each menu items follows.