1, a constant, also known as a "constant", refers to a quantity whose value will not change in a program or mathematical operation. Constants can be values represented by numbers, letters or other symbols. Once a value is given, it cannot be modified while the program is running.
2. Variables, also known as "variables", refer to the quantities whose values can be changed during the running of a program. Variables are used to store data and can be given new values when executing programs to reflect changing data or calculation results. In short, constants and variables represent invariants and variables respectively under certain conditions.