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const int max = 15;
int a[max]; /* Invalid declaration outside of a function */
const int *p;
/* A const-qualified object can have its address taken. */
p = &max;
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const-qualified objects are likely to incur some runtime overhead [Saks 2001b]. Most C compilers, for example, allocate memory for const-qualified objects. const-qualified objects declared inside a function body can have automatic storage duration. If so, the compiler will allocate storage for the object, and it will be on the stack. As a result, this storage will need to be allocated and initialized each time the containing function is invoked.
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# define identifier replacement-list
defines an object-like macro that causes each subsequent instance of the macro name to be replaced by the replacement list of preprocessing tokens that constitute the remainder of the directive.
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