A constant is a variable that has a value which cannot be changed once the constant has been assigned. This allows the compiler to enforce that the variable’s value is not changed anywhere in the code by mistake.
A variable can be made into a constant by adding the const keyword either before or after the data type. This modifier means that the variable becomes read-only, and it must therefore be assigned a value at the same time as it is declared. Attempting to change the value anywhere else results in a compile-time error.
const int var = 5;int const var2 = 10; // alternative order