## Common Spreadsheet Format

js-xlsx conforms to the Common Spreadsheet Format (CSF):

### General Structures

Cell address objects are stored as `{c:C, r:R}` where `C` and `R` are 0-indexed
column and row numbers, respectively.  For example, the cell address `B5` is
represented by the object `{c:1, r:4}`.

Cell range objects are stored as `{s:S, e:E}` where `S` is the first cell and
`E` is the last cell in the range.  The ranges are inclusive.  For example, the
range `A3:B7` is represented by the object `{s:{c:0, r:2}, e:{c:1, r:6}}`. Utils
use the following pattern to walk each of the cells in a range:

```js
for(var R = range.s.r; R <= range.e.r; ++R) {
  for(var C = range.s.c; C <= range.e.c; ++C) {
    var cell_address = {c:C, r:R};
  }
}
```