TIdDecoder = class(TIdBaseComponent);

TIdDecoder is a TIdBaseComponent descendant that is the ancestor for Indy classes that perform decoding operations on String values to either String- or Stream-based destinations. 

Applications do not normally create instances of TIdDecoder, and instead use one of the descendant classes that implements a specific decoding algorithm. TIdDecoder can be used an as ancestor for classes that utilize a unique decoding algorithm and also adhere to the Indy coder framework. 

Descendants of TIdDecoder include TIdDecoder4to3 and TIdDecoderQuotedPrintable.