The screen you see when editing a Currency along with a description of the fields and their purpose is shown below.

currencies currency edit

Currency name

Enter the currency name

Published

Set to Yes to publish the currency or No to unpublish it

Exchange Rate

Enter the value of the exchange rate in case of a fix rate, or enter 0 to use a dynamic rate.
Dynamic rates uses the currency rates provided by  the European Central Bank.

Code 2 letters, Code 3 letters, Numeric Code

Those 3 codes are  the ISO 4217 standard currency codes. They are used for the dynamic rates and by the payment plugins.

Currency Symbol

The currency symbol will be the one displayed along with the prices. Even if a standard exists for the currency symbols exists, they are only use for display.

Decimals

Decimal is the number of decimal used to display prices  for this currency.

Decimal Symbol

The decimal symbol is either "." or "," depending on the currency.

Thousands Separator

Depending on the currency the Thousands separator is usually a "space", or a "." .

Positive Format, Negative Format

The prices will be displayed follwing that pattern

For Positive or Negative Format, use

  • {sign} for the algebraic sign,
  • {number} for the value and
  • {symbol} for the currency

as placeholder, all html tags are allowed, except the character | is not allowed 
For example

{sign} {number} {symbol}

will display a price like "+ 42,23 €"