形式参数
函数的参数，形式参数，被当作该函数内的局部变量，如果与全局变量同名它们会优先使用。下面是一个实例：
实例

include

/ 全局变量声明 /
int a = 20;

int main ()
{
/ 在主函数中的局部变量声明 /
int a = 10;
int b = 20;
int c = 0;
int sum(int, int);

printf ("value of a in main() = %d\n", a);
c = sum( a, b);
printf ("value of c in main() = %d\n", c);

return 0;
}

/ 添加两个整数的函数 /
int sum(int a, int b)
{
printf ("value of a in sum() = %d\n", a);
printf ("value of b in sum() = %d\n", b);

return a + b;

}
当上面的代码被编译和执行时，它会产生下列结果：
value of a in main() = 10
value of a in sum() = 10
value of b in sum() = 20
value of c in main() = 30