Boxes is a text filter that can draw any kind of box around its input text. Box design choices range from simple boxes to complex ASCII art. A box can also be removed and repaired, even if it has been badly damaged by editing of the text inside. Since the generated boxes may be open on any side, the program can also be used to create regional comments in any programming language. New box designs of all sorts can easily be added and shared by appending to a free format configuration file. In addition to being a command line tool, Boxes integrates well with any text editor that supports filters.
GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content: text, mathematics, graphics, interactive content. TeXmacs can also be used as an interface to many external systems for computer algebra, numerical analysis, and statistics. New presentation styles can be written by the user and new features can be added to the editor using Scheme.
HCC is character filter which replaces certain characters by other characters one by one, according to a translation table. It is useful for converting plain texts from one character set to another. Currently available filters include win1250 to ISO-8859-2, win1250 to ASCII (ISO-8859-1), ISO-8859-2 to win1250, and ISO-8859-2 to ASCII (ISO-8859-1). You may get better results with "iconv" utility which is part of glibc.