ANSI C supports data type qualifier const to declare a variable as constant in a C program. We have already learned that constants in C language have fixed values that do not change during the program.
If we declare a variable as a constant, the value of that variable remains constant during the execution of the program.
We use the keyword const to declare a variable as a constant. For example,
const int pass_mark = 45;
The above code tells the compiler that the value of the variable should not be changed during the program execution.