Data types are qualitative, quantitative; fixed class, fixed order, fixed distance, fixed ratio and so on. Qualitative data, including categorical data and sequential data, is a set of textual data that expresses the nature of things and specifies the categories of things, which can not be quantified, but can only be characterized.

Categorical data is formed by the measurement, the performance of the category, can not distinguish the order. Data is the result of facts or observations, is the logical generalization of the objective things, is used to represent the objective things of the unprocessed raw material. Fixed-order data is formed by the fixed-order scale measurement, manifested as a category, can be sorted, can only compare the size, can not perform mathematical operations.

Fixed-distance data is formed by fixed-distance scale measurements, manifested as numerical values, can be added, subtracted to accurately calculate the data. In computer science, data is the general term for all media that can be entered into a computer and processed by a computer program as symbols, and is a generic term for numbers, letters, symbols, and analog quantities that are used to enter into an electronic computer for processing and that have a certain significance.