NumberConverter is for the most part self explanatory.
Run it with the flag -h for command-line usage information.

By default, it reads a configuration file named .numberconverterrc
(except on MS Windows, where it is named NumberConverterInit).
Lines beginning with a cross-hatch (#) character are ignored.
The following flags may be set in this file:

Balloon_Help_P
Generate_Roman_With_Bar_P
Input_Base
Output_Base
General_Group_Size
First_Group_Size
Separator_Character

The first two flags are Booleans and may be set to any of the obvious Boolean values,
e.g. 1, T, Yes, True, on for True, 0, F, No, False, off for False.

Case is irrelevant. The underscores may be omitted or replaced with hyphens or spaces.

The syntax is: set <variable> <value>, e.g.

set Input_Base 8
set Balloon_Help_P 0