data structure added in manual

Author: prathameshnium

docs/User_Manual.md

@@ -444,6 +444,22 @@ PICA uses standard VISA resource strings. While the defaults below are common, u
 
 This project is manually backed up weekly to a [GitLab repository](https://gitlab.com/prathameshnium/pica-python-instrument-control-and-automation).
 
+### 8.4 Data File Format
+
+The data file includes a commented header line (starting with `#`) that contains metadata, such as the sample name. This is followed by a header row with column names and then the data rows.
+
+This structure makes it easy to import the data into various analysis programs like Origin, or to parse it programmatically with libraries like Pandas.
+
+**Example: Ultra Low Resistance (I-V) Module**
+
+```
+# Sample: Delta_Test_10ohm
+Set Current (A),Measured Voltage (V),Resistance (Ohm)
+-1.000000e-05,-1.037917e-04,1.037917e+01
+-9.797980e-06,-1.017006e-04,1.037975e+01
+```
+Most other data files generated by PICA follow a similar structure.
+
 ## 9. Citation & Open source
 
 **Collaborative Ecosystem:**