Explain the origin of variables
Explanatory variables, derived from mathematics, are abstract concepts that can store calculation results or express numerical values in computer language. Interpreted variables can be accessed by interpreting the variable name. In imperative languages, explanatory variables are usually variable; But in purely functional languages (such as Haskell), explanatory variables may be immutable. In some languages, explanatory variables may be clearly defined as abstractions that can represent the state of variables and have storage space (such as in Java and VisualBasic).