梵蒂冈之花
这不是必需的，但不使用原型是不好的做法。使用原型，编译器可以验证您正在正确地调用函数(使用正确的参数编号和类型)。没有原型，就有可能拥有以下内容：// file1.cvoid doit(double d){
....}int sum(int a, int b, int c){
return a + b + c;}这是：// file2.c// In C, this is just a declaration and not a prototypevoid doit();int sum();int main(int argc, char *argv[]){
char idea[] = "use prototypes!";
// without the prototype, the compiler will pass a char *
// to a function that expects a double
doit(idea);
// and here without a prototype the compiler allows you to
// call a function that is expecting three argument with just
// one argument (in the calling function, args b and c will be
// random junk)
return sum(argc);}