const

The const keyword can be used to define constants instead of using #define:

	const int			count=5;

However, it is most useful when combined with function prototypes. Routines that should not be modifying parameters can define the parameters as constants, and the compiler will then give errors if the parameter is modified. Because C passes parameters by value, most parameters don't need to be declared as constants. If the parameter is a pointer, though, it can be declared to point to a constant object:

	int strlen(const char *s)
 	{
 		...
 	}

Any attempt to change the string by strlen() is an error, and the compiler will catch the error.