wdata-format-concept.md

@@ -161,6 +161,17 @@ The following formats are allowed:
   * `npy`: binary files are *numpy* arrays. (_C library supports only read mode._)
   * `dpca`: (*deprecated*) previous format of cold atomic codes. The binary file contains a header of size 68B, where additional info about the file content is stored. For this format, *wdata* lib provides only reading functionality.  
 
+Examples
+```bash
+# Each variable is represented as separate file of name <prefix>_<name>.<format>
+# tag       name        type        unit        format 
+var           v1      vector          vF          wdat    # all fields are specified
+var           v2     complex          eF                  # variable with specified unit (eF) and default format (wdat)
+var           v3        real                              # this variable has no unit (none) and default format (wdat)
+var           v4      vector        none                  # this variable has no unit (none) and default format (wdat)
+var           v5      vector                     wdat     # this variable has no unit (none) and spefified format (wdat)
+```
+
 ## Links
 It is an alternative name for a given variable. The entry has a form
 ```
@@ -172,7 +183,7 @@ var         density             real              none           wdat
 ```
 while another user, in his/her code, uses the name `rho` for the same variable. To maintain the operability of the code that uses the variable `rho`, the second user can add an entry to `*wtxt` file in the form
 ```
-link        rho        density
+link        rho        density    # rho is the same as variable density
 ```
 
 ## Constants  
@@ -180,9 +191,21 @@ Typically, besides variables, we have some useful constants during the data anal
 ```
 const            name            value             unit
 ```
-For example:
+Examples:
+```bash
+# Constants 
+# tag       name        value       unit
+const      alpha     0.007297                   # constant with no unit (none)
+const         pi       3.1415       none        # constant with no unit (none)
+const         m           0.1         kg        # constant with unit (kg)
 ```
-const              eF              0.5             
+
+## Txt files
+The wtxt file can also contain info about additional text files associated with the dataset. 
+Note, beside this info in the wtxt file, C library do not provide any extra functionality for text files.  
+```bash
+# This tag indicates that the file prefix_myfile.txt also belongs to the dataset
+# The tag is used only by VisIt for now
+txt         myfile.txt
 ```
 
-See [here](https://gitlab.fizyka.pw.edu.pl/wtools/wdata/-/wikis/Tags) for a complete list of tags. 
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