On 23 November 1979, the government of Comoros signed the "Accord de coopération monétaire entre la République Française et la République fédérale islamique des Comores", a monetary cooperation agreement with France, making Comoros part of the franc zone (but not part of the CFA franc zone). This agreement provided for the establishment of a system of fixed parity between the French franc and the Comorian franc and free convertibility between the two currencies, guaranteed by the Comorian central bank's opening of an operations account ("compte d'operation") at the French Treasury (Trésor public) to handle all exchange transactions. Sixty-five percent of the foreign exchange reserves of Comoros are held in euros in this account. This account is similar to overnight deposits with the French Treasury: it may bear interest and may, in special circumstances, post a negative balance. However, to prevent this account from showing a lasting overdraft, a number of preventative measures have been set up.