It’s a best practice to prefix all computed fields with “c_” (e.g., c_Region) for the following reasons:
1) Computed fields are not original data, and you should always keep this in mind. You should scrutinize the values in computed fields carefully, especially when you discover data or relationships that you were not expecting.
Before you raise an audit issue based on a computed field, check your expressions and ensure the resulting data is correct. This is especially important when a computed field is used to create other computed fields.
For an introduction to computed fields, see this.
2) This ensures computed fields are grouped together on a table layout for easy reference and tweaks.
Table layouts list the fields in alphabetical order, so computed fields (because they begin with c_ ) tend to float to the top of the layout (see below).
Do you prefix your computed fields? Why or why not?