property Encoding: TIdEncoding;

Encoding is a TIdEncoding property identifies the default encoding used when writing values stored in the buffer. The default value for Encoding is enANSI, as assigned in the constructor for the buffer instance. 

The value assigned to Encoding is used in an overloaded version of the Write method that accepts an optional encoding value. When the value is omitted (or contains enDefault), the value in the Encoding property is used encode the bytes written to the buffer instance.