LMOD-QuickReference-Guide.md

@@ -62,6 +62,30 @@ To check which actions would be taken with loading a specific module, you can us
 
 #### Searching modules
 
+From the old TCL module system you are used to having categories, like DEVELOP, CHEMISTRY etc. pp. So if you are looking for chemistry software, you would load the CHEMISTRY module and see what software is installed. This is what is called a "Categorized Module Naming Scheme" or CMNS for short.
+With LMod, this has changed to a Hierarchical Module Naming Scheme (HMNS), which loads additional module paths whenever a module is loaded that was used to build software (e.g., OpenMPI only becomes visible if you have loaded a compiler that was used to build that version of OpenMPI). This is in contrast to CMNS. But as we know, many users were happy with these categories. So we added the "category" command to LMod:
+
+```sh
+> module category
+
+To get a list of every module in a category execute:
+   $ module category Foo
+
+--------------------------------------------------------------------------------------- List of Categories ----------------------------------------------------------------------------------------
+cfd chem devel io material math perf tools
+```
+which shows you the categories which are agreed with the colleagues of the TU Darmstadt. Which software is hidden behind the categories can be seen by entering (e.g. for chemistry) the following:
+
+```sh
+> module category chem
+
+To learn more about a package and how to load it execute:
+   $ module spider Bar
+
+---------------------------------------------------------------------------------------------- chem -----------------------------------------------------------------------------------------------
+Gaussian (6) PETSc (1) QuantumESPRESSO (1)
+```
+
 If you don't know how a specific module is called or a module is currently not visible to you and you want search for a software, you can use the `spider` option.
 
 ```sh