Differences between the new code and the old code:

1. Command structure:
   
   • New: Uses a single /monnaie command with subcommands (rate, exchange, admin).
   • Old: Uses a specific /monnaie exchange command.
2. Conversion rate:
   
   • New: Dynamic rate that fluctuates with time and exchanges.
   • Old: Fixed rate of 24.
3. Additional functions:
   
   • New: Adds formatNumber(), getTauxConversion(), updateTauxConversion().
   • Old: Doesn't have these functions.
4. Exchange for other players:
   
   • New: Allows exchanging for oneself or for another player.
   • Old: Exchange only for oneself.
5. Administrative commands:
   
   • New: Includes admin commands to set the rate.
   • Old: No administrative commands.
6. Calculation of money obtained:
   
   • New: Uses a complex formula based on the dynamic rate.
   • Old: Simple multiplication by the fixed rate.
7. Initialization and management of global variables:
   
   • New: Initializes {taux_conversion} and {dernier_echange} on load.
   • Old: No initialization of global variables.
8. Automatic announcements:
   
   • New: Broadcasts the rate every 5 minutes.
   • Old: No automatic announcements.
9. Tab completion:
   
   • New: Includes a tab completion function for commands.
   • Old: No tab completion.
10. checkBalanceForOther function:
    
    • New: Adds a function to check the balance when exchanging for another player.
    • Old: Doesn't exist.
11. Error handling and debugging:
    
    
    • New: More debug messages and error handling.
    • Old: Less detailed in terms of debugging.

The new code is more complete, flexible, and offers more features for managing a dual currency system on a Minecraft server.