The programmes have been developed gradually, according to my needs and possibilities. Included are also similarly developed programmes of my colleagues, who agree with their spreading under the same GNU General Public License [2]. We have used mostly algorithms from a booklet by Zdeněk Pokorný [5] (who himself used the book by Jan Meeus [6]) and from text by Jana Vondrák in [7].
As the programmes became more complicated, or as the author could not
remember algorithms of old programmes, a need for some documentation
emerged, at least in the form of comments in the source
codes. In spite of that, the comments remained mostly quite
insufficient, and the programmes are very far from the ideal of
literate programming, as formulated and made true by Donald
Knuth (author of programmes like WEB and TEX[15]).
Further, the programmes have been supplemented to behave well, like
(e.g.) programmes of MS-DOS which explain their meaning and use when
being started a suitable way. These instructions how to use the
programme are contained at the beginning of its text.
Some time ago, I have noticed two problems of Borland Turbo Pascal
when run with or without numeric co-processor. The first one concerns
different ways of rounding. Pascal itself rounds real numbers ending
.5 to a greater absolute value, whereas numeric co-processor to an
even number. I have changed in some programmes the rounding procedure
to a third possibility, namely always to a greater value (by a
function RoundUp). The second problem concerns formatting. With
co-processor, all unformatted real numbers are output as extended,
with e.g. four digits in exponent. Some formatting procedures at the
beginning of str_num unit overcome different behaviour of
different hardware.
The programmes are English-written, with few exceptions. Why is that
so, when most of the users are speaking Czech? The main reason is,
that the author hates disabled Czech without diacritics, and that
Czech diacritics has not just one possibility how to be implemented
in the computers. The problem of two main MS-DOS-based ``code pages''
can be solved by the programme CS_Conv. But the English programmes
are easier to read, when names of variables, subroutines and comments
are English as well as the programming language. And each potential
user of these programmes surely reads English, with some effort at
least.
If you make some programme better, and you suppose, that your adaptation may suit another people as well, please give them whole this package including your addition. I welcome you sending the modified programme me as well. I will gladly discard the original work and replace it by the same-named version by you in our set.
As follows from the License [2], everybody can modify the programmes and use their parts in her/his own programmes. If such programmes are spread further, they are obliged to remain free software subject to the same Public License.
If the change of a programme concerns only
solar_ut unit),