C语言知识点整合（1）

#include <stdio.h>
#include <windows.h>

int main()
{
	printf("(are you ok \x030 ??)\n"); //三字母词
	system("pause");
	return 0;
}

int main()
{
	printf("%d\n", sizeof(char));
	printf("%d\n", sizeof(short));
	printf("%d\n", sizeof(int));
	printf("%d\n", sizeof(long));
	printf("%d\n", sizeof(long long));
	printf("%d\n", sizeof(float));
	printf("%d\n", sizeof(double));
	printf("%d\n", sizeof(long double));
	system("pause");
	return 0;
}

int main()
{
	int num = 0;
	const int c_num = 0;
	num = 10;
	c_num = 20; //当const 修饰一个标识符的时候,它具有常属性，不能被直接改变
	system("pause");
	return 0;
}

int main()
{
	const int sz = 10;
	int arr[10] = { 0 };
    int arr2[sz] = { 0 };//当const 修饰一个标识符的时候，这个标识符依然是一个变量
	system("pause");
	return 0;
}

#define PAI 3.14  //没有；
int main()
{
	int radius = 1;
	double area = PAI*radius*radius;
	printf("%f\n", area);  //注意是%f
	system("pause");
	return 0;
}

enum Sex
{
	MALE,
	FEMALE,
	SECRET
};
int main()
{
	printf("%d\n", MALE);
	printf("%d\n", FEMALE);
	printf("%d\n", SECRET); //枚举常量从0开始
	system("pause");
	return 0;
}

void test()
{
	static int num = 0;  //num变为全局变量
	num++;
	printf("%d\n", num);
}
int main()
{
	int i;
	for (i = 0; i < 10; i++)
	{
		test();
	}
	system("pause");
	return 0;
}

int main()
{
	int i = 43;
	printf("%d\n", printf("%d", printf("%d", i))); //printf的返回类型是int,且处理方式为从右至左
	printf("%d\n", i);
	system("pause");
	return 0;
}