TWC uses quadrature amplitude modulation (QAM) of (I believe) ATSC signals. DVB-C appears to be the European standard for digital broadcast over cable. Why do you ask?
FYI, TWC will provide the equipment necessary to view their digital signals (at a cost) and will not authorize any non cable card compliant device to decrypt any encrypted signals.
They typically use Scientific Atlanta Digital Decoder boxes which use the Scientific Atlanta PowerView System for Encryption of the QAM channels.
In a few markets where they have purchased the system which was a Motorola based system, they have continued to use Motorola which uses their DigiCipher II encryption.