The distinction between constants and variables

In the program, constants and variables always appear, and there will always be some unclear states in the definition of the two.
Constants are constant during the running of the program, that is, the content entered before the running of the program has not changed during and at the end of the running of the program, and the unchangeable quantity is also a constant.
Variable : The initial value is changed during the running of the program. Even if the value does not change, as long as the amount that can be changed during operation, it is also a variable.