In good old days, C programmers would use preprocessor directive to define constants. e.g. #define s 10 But we know now that, as compiler never gets to see these, preprocessor statements are error prone. Hence we have const s. A constant - defined with keyword const promises that this entity is never going to change. And if we accidentally modify a const, compiler throws an error. Let us look at an example. #include<iostream> using namespace std; int main () { int a = 10 ; const int b = 12 ; a ++ ; b = 18 ; } When we compile this program, compiler tells us that default.cpp: In function ‘int main()’: default.cpp:8:7: error: assignment of read-only variable ‘b’ b = 18; So it is catching the error that we are trying to modify a const. Whenever a local variable or parameter need not be modified, declare it as a const. Yes, we can make even parameters as constant. We can make objects constant or even me...
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