wdata-format-concept.md

@@ -8,7 +8,7 @@
 * Data is convenient for copying between computing systems.  
 * It allows for easy extraction/copying of selected variables.
 
-**W-data** format **is not a library**. It is only a **concept**. It specifies how the data should be saved or read. It means that you do not need to use any external libraries to be able to read or write. It is sufficient to use standard I/O functions to work with this format. We provide within this repository libraries written in C or in python just for convenience. The example code demonstrating this concept can be found here [
+**W-data** format **is not a library**. It is only a **concept**. It specifies how the data should be saved or read. It means that you do not need to use any external libraries to be able to read or write. It is sufficient to use standard I/O functions to work with this format. We provide within this repository libraries written in C or in Python just for convenience. The example code demonstrating this concept can be found here [
 c-examples
 /example-write-low-level.c](https://gitlab.fizyka.pw.edu.pl/wtools/wdata/-/blob/master/c-examples/example-write-low-level.c). The concept is described below. 
 
@@ -31,11 +31,14 @@ nz                       32   # lattice
 dx                        1   # spacing
 dy                        1   # spacing
 dz                        1   # spacing
+x0                      -12   # origin of x-axis
+y0                      -14   # origin of y-axis
+z0                      -16   # origin of z-axis
 datadim                   3   # dimension of block size: 1=nx, 2=nx*ny, 3=nx*ny*nz
-prefix                 test   # prefix for files belonging to this data set, binary files have names `prefix_variable-name.format`
+prefix                 test   # prefix for files belonging to this data set`
 cycles                   10   # number of cycles (measurements)
 t0                        0   # time value for the first cycle
-dt                       0.1   # time interval between cycles. If `dt` negative then time step is varying and is read from binary file `prefix__t.wdata`
+dt                        1   # time interval between cycles
 
 # variables
 # tag                  name                    type                    unit                  format
@@ -53,7 +56,15 @@ link              current_b               current_a
 const                    eF                     0.5                     MeV
 const                    kF                       1                    1/fm
 ```  
-According to our experience, three [types of variables](https://gitlab.fizyka.pw.edu.pl/wtools/wdata/-/wikis/Data%20types) (`real`, `complex`, `vector`) are sufficient and cover more than 90% of applications. However, we have implemented single-precision (`float` in C notation) types denoted as `real4`, `complex8`, and `vector4`. To be consistent with the notation, one can use `real8`, `complex16` or `vector8` exchangeable for `real`, `complex`, `vector`. 
+According to our experience, three types of variables (`real`, `complex`, `vector`) are sufficient and cover more than 90% of applications. The variables can be stored either in double or float precision.
+
+| type      | float    | double      |
+|-----------|----------|-----------|
+| real      | `real4`    | `real`, `real8`  |
+| complex   | `complex8` | `complex`, `complex16` |
+| vector    | `vector4`  | `vector`, `vector8`  |
+
+However, we have implemented single-precision (`float` in C notation) types denoted as `real4`, `complex8`, and `vector4`. To be consistent with the notation, one can use `real8`, `complex16` or `vector8` exchangeable for `real`, `complex`, `vector`. 
 
 Binary files store data as row arrays called `datablocks`:  
 ![datablocks](uploads/4d9d6260250707f665bda6e6c4e921cf/datablocks.png)