Handling the programmes

Some programmes explain how to use them, whenever they are run without parameters (this applies for those ones, which always need some parameters). Another ones offer instructions to users, if at least one of parameters is ? (or /? or -?). Programs with long explanation should give a possibility to write it into a file instead to a screen. Mostly the standard redirecting of the output can be used, as fGCVS >> fGCVS.hlp. Some programmes, which have to react on each key during their work, make redirecting impossible, however (the crt tool of Borland Turbo Pascal language is guilty). These programmes create a file *.hlp, when asked to do that by /h (or -h) parameter. For example, graph_d -h.

All of the programmes are controlled by the parameters on the command line. Saying parameter, we understand a ``word'', single parameters are (as usual with real words) separated by spaces. Controlling programmes by parameters is comfortable thanks to the fact, that the command can be repeated many times with just small changes of parameters (directly from MS-DOS you can do it easily, when the DOSKey /insert runs). Even greater advantage is a possibility to make batch files (i.e. *.bat), where some parameters are defined already (e.g., your geographical coordinates).

The above-mentioned programme graph_d is one of few exceptions. If you use it for polynomial (usually linear) regression of data, or if you try to find their axis of symmetry, then the programme asks you some questions also in the course of the work. This conversation is implemented in a rather simple way (it is an old programme already, what appears also through an unusual shape of its command-line parameters), but it suffices its task.

Most programmes in our set, which produce a graphic output on the screen, can simultaneously create a corresponding file with a picture in L^ATEXor PostScript language (file *.eps). Using them, you can produce prints with unlimited resolution, and modify them before the print by any text editor. This is a notable advantage over those commercial programmes which offer a mere possibility to copy a screen on the paper. As far as PostScript [13] is concerned, it is language of all advanced printers and photo-setting machines. If you have none, install GhostScript (http://www.cs.wisc.edu/ ghost) into your computer. Its supplement PSView can be then used for comfortable viewing of PostScript outputs on the screen.

As the graphic screen may pose problems in some cases (e.g., on Linux text console), the graphic programmes may be converted to text versions, which produce just the PostScript output (there are conversion batch files available).