小学生四则运算练习器，用户可以选择进行加减乘除任意一项，也可以选择退出，然后每次计算后会提示正确与否，最后计算总分然后并给出评语。

⑴ 用户可以从菜单中选择某种运算进行练习。具体包括：加法，减法，乘法，除法；也可以退出程序.

⑵ 用户可以指定每次练习的题目数量、设置练习的总分；

⑶ 每小题练习后给出结果正确与否的提示；一次练习结束后，给出用户所得的总分；

⑷ 用户选择退出时，可退出系统。

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define num 10
void showmain();
int getchoice();
int add();
int sub();
int mul();
int div();
void prnscore();
void exit();

//退出系统
void exit()
{
	printf("再见啦!\n");
}

//主菜单
void showmain()
{
	printf("*************************\n");
	printf("小学生数学联系系统\n");
	printf("     1  加法    \n");
	printf("     2  减法    \n");
	printf("     3  乘法    \n");
	printf("     4  除法    \n");
	printf("     0  退出    \n");
	printf("*************************\n");
	printf("请选择(0-4):");

}
//选择模块
int getchoice()
{
	int i;
	scanf("%d", &i);
	return i;
}

//加法
int add()
{
	int x, y, result, score = 0;
	printf("小朋友,开始做题了!!!\n");
	srand((unsigned)time(NULL));
	int i = 0;
	while (i < num)
	{
		x = rand() % 100;
		y = rand() % 100;
		printf("%d+%d=", x, y);
		scanf("%d", &result);
		if (result == x + y)
		{
			printf("做对啦!!\n");
			score += 10;
		}
		else
		{
			printf("做错了,继续加油!!!\n");
		}
		i++;
	}
	return score;
}


//减法
int sub()
{
	int x, y, result, score = 0;
	printf("小朋友,开始做题了!!!\n");
	srand((unsigned)time(NULL));
	int i = 0;
	while (i < num)
	{
		x = rand() % 100;
		y = rand() % 100;
		printf("%d-%d=", x, y);
		scanf("%d", &result);
		if (result == x - y)
		{
			printf("做对啦!!\n");
			score += 10;
		}
		else
		{
			printf("做错了,继续加油!!!\n");
		}
		i++;
	}
	return score;
}

//乘法
int mul()
{
	int x, y, result, score = 0;
	printf("小朋友,开始做题了!!!\n");
	srand((unsigned)time(NULL));
	int i = 0;
	while (i < num)
	{
		x = rand() % 100;
		y = rand() % 100;
		printf("%d*%d=", x, y);
		scanf("%d", &result);
		if (result == x * y)
		{
			printf("做对啦!!\n");
			score += 10;
		}
		else
		{
			printf("做错了,继续加油!!!\n");
		}
		i++;
	}
	return score;
}

//除法
int div()
{
	int x, y, result, score = 0;
	printf("小朋友,开始做题了!!!\n");
	srand((unsigned)time(NULL));
	int i = 0;
	while (i < num)
	{
		x = rand() % 100;
		y = rand() % 100;
		if (y == 0)
		{
			continue;
		}
		printf("%d/%d=", x, y);
		scanf("%d", &result);
		if (result == x / y)
		{
			printf("做对啦!!\n");
			score += 10;
		}
		else
		{
			printf("做错了,继续加油!!!\n");
		}
		i++;
	}
	return score;
}

//打印分数
void prnscore(int score)
{
	printf("这次练习你一共得分;%d\n", score);
	if (score >= 80)
		printf("干得漂亮!!!\n");
	else
		printf("同志,继续加油!!!\n");
}


int main()
{
	int choice = 0;
	int score = 0;
	while (1)
	{
		showmain();
		score = 0;
		choice = getchoice();
		switch (choice)
		{
		case 1:score = add(); break;
		case 2:score = sub(); break;
		case 3:score = mul(); break;
		case 4:score = div(); break;

		}
		if (choice == 0)
		{
			break;
		}
		prnscore(score);
	 }
	exit();
}