If a function doesn't expect any parameters, you might be tempted to leave
its parameter list blank. But it's better to put void in its parameter list, as
shown here:
void beep( void );
The void in parentheses specifies that the beep function requires no para-meters. If you leave the parentheses empty, the compiler draws no conclusion about what parameters the function takes and won't be able to detect an error if you mistakenly pass an argument to the function.