1. "Computer Data Security" firstly belongs to the category of Computing Technology, Computer Technology, and its classification code in the CLC is TP2.In the CLC, look for TP category - TP309 Security and Confidentiality - TP309.2. Computer data security, therefore, the classification number of "computer data security" is TP309.2. When writing in the thesis, the "classification number" is usually labeled after "keywords". In the thesis, "CCTN" is usually labeled after "keywords". The way to write: [CCTC]: TP309.2 or CCTC: TP309.2. "CCTC" can be found in the reading room of the university library, or on the Internet.