Constants

When you don't want others (or yourself) to override existing variable values, use the const keyword (this will declare the variable as "constant", which means unchangeable and read-only):

    
        #include<stdio.h>
        
        int main() {
            const int myNum = 15;
            myNum = 10;
            printf("%d", myNum);
            return 0;
        }
    

You should always declare the variable as constant when you have values that are unlikely to change:

    
        #include<stdio.h>
        int main() {
        const int minutesPerHour = 60;
            const float PI = 3.14;
            printf("%d\n", minutesPerHour);
            printf("%f\n", PI);
            return 0;
        }
    

When you declare a constant variable, it must be assigned with a value:

    
        Like this:
        const int minutesPerHour = 60;

        This however, will not work:
        const int minutesPerHour;
        minutesPerHour = 60; // error
    

    
        #include<stdio.h>

        int main() {
            const int minutesPerHour;
            minutesPerHour = 60;
            printf("%d", minutesPerHour);
            return 0;
        }