Some existing LaTeXGlossary.tex#LaTeX documents can be opened directly by the program. However, a number of constructs need modification with an ASCII editor before they can be opened. In particular, statements of the form \newcommand and \def usually cause problems. As a defensive measure, the program expands these statements, which is generally not what you want.
In general, if LaTeX has a construct that differs from plain TeX (for example, array vs matrix), use the LaTeX construct.
If a document is successfully read by the program, modified, and then saved, the command \input tcilatex is added to the preamble.
To open a LaTeX document