三.数据类型

三.数据类型

1.数据类型的大小,所占字节数

//sizeof  关键字  计算变量或数据类型所占的字节个数
char       1
bool       1
void       
int        4
long int   4
short      4
float      8
double     8
long long  8

2.逗号表达式
所有的运算符里面,逗号表达式的优先级最低的,从左到右,顺序运算

#include<stdio.h>
int main()
{
	int a = 1, b = 2, c = 3;
	int x = 0;
	x = (a + b, b + 2, c + 3);//只输出最右边的值
	printf("%d", x);
	return 0;
}
//输出: 6 

//法一:
#include<stdio.h>
int main()
{
	int n = 0, sum=0;
	printf("enter number:");
	do {
		scanf_s("%d", &n);
		sum += n;

	} while (n != 0);
	printf("%d", sum);
		return 0;
}
//法二:
#include<stdio.h>
int main()
{
	int n = 0, sum = 0;
	printf("enter number:");
	do {
		sum += n;
	} while (scanf_s("%d", &n),n != 0);
	printf("%d", sum);
	return 0;
}```

```c
//7.1取模
int main()
{
	int x = 1;
	x = 20 % 12;
	printf("%4d\n", x);
	x = -20 % 12;
	printf("%4d\n", x);
	x = 20 % -12;
	printf("%4d\n", x);
	x = -20 % -12;
	printf("%4d\n", x);
	return 0;

}

//7.2  *=    
int main()
{
	int a = 3, b = 4, c = 5;
	a *= b + c;
	printf("a=%d\n", a);
	return 0;
}

//7.3  三目运算符  条件表达式 ? 表达式 1 : 表达式 2
int main()
{
	int a = 10, b = 20, c = 30;
	c = a < b ? a : b;
	printf("%d", c);
	return 0;
}

//7.4  前置++和后置++的区别
int main()
{
	int a = 0;
	int b = 0;
	int c, d;
	c = ++a;//先加再用
	d = b++;//先用再加
	printf("c=%d  d=%d", c, d);
	return 0;
}