100~200之间素数

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main()
{
int a, b, c = 0;//定义整型变量a，b，c并给c初始化赋值
for (a = 100; a <= 200; a++)//for循环体，a初始值100，a小于201，a自加1

{

	for (b = 2; b < a; b++)//for循环体，b初始值2，b小于a，b自加1
	{
		if (a%b == 0)
			break;//如果a能除余b，跳出循环
		else
		if (b == a - 1)
			c = 1;
	}
	if (c == 1)
	{
		printf("%d\n", a);
		c = 0;
		system("pause");
	}
}

}

输出乘法口诀表

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main()
{
{ int a, b;
for (a = 1; a <= 9; a++)

{
	for (b = 1; b <= 9; b++)
		printf("%d*%d=%d\n", a, b, a*b);
}


	printf("\n");
	system("pause");

}return 0;
}![在这里插入图片描述](https://www.icode9.com/i/ll/?i=201909231435182.png?,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQyNjY0NjM2,size_16,color_FFFFFF,t_70)

1000~2000间闰年

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int main()
{
int x;
for (x = 1000; x <= 2000; x++)

	if (x % 400 == 0)

		printf("%d\n是闰年", x);

	else{
		if (x % 100 != 0 && x % 4 == 0)
			printf("%d是闰年", x);
	}
	system("pause");
	printf("%d\n不是", x);}