The actual conversions themselves are held in a separate text files contained within the application directory. For example, Length.txt, Volume.txt. To maintain the conversions simply edit the appropriate file in a text editor such as Notepad.
Each conversion takes one line, the layout fo which is:
Unit The source or destination unit, e.g. Metres.
PrimaryUnit? A flag to denote the for a category. Only one unit per category should have this flag set.
ExpOrMult Calculation is an expression (True) or a multipleer (False)
Multiplier The quantity by which a given quantity must be multiplied to give the equivalent in primary units. So for example, to convert feet to metres (primary unit for Length) you multiply by 0.3048.
All conversion "multipliers" are on the basis of conversion the for the category. So for example if you want to add a new Length conversion then simply work out how many metres (the primary unit in the category) there are in your chosen unit and use this value as the multiplier.