Definition explanation: (1) Abstract data type: refers to a mathematical model and a set of operations defined on the model. The definition of abstract data type only depends on its logical characteristics, and has nothing to do with its expression in the computer, that is, no matter how its internal structure changes, as long as its mathematical characteristics remain unchanged, it will not affect other external uses. (2) Representation and implementation of abstract data types: they can be represented and implemented by inherent data types. That is, the new structure is interpreted by using the data types stored in the processor, and the new operations are combined by the implemented operations. (3) Take the linear table as an example, the relationship between them: the definition of abstract data type linear table is only a linear table abstracted in logical order, and its storage structure has not been involved, but the representation is to establish the storage structure of linear table, and the realization is to write a specific algorithm through some specific programming languages and get the results through the algorithm. To sum up, their relationship is a process from abstract logical order to concrete implementation algorithm.