C语言作业,编写一个简单的计算器,实现加减乘除运算，谢谢大家

#include
#include
#include

int cls()
{
	system("cls");
                 return 0;
}
int pause()
{
	system("pause");
                 return 0;
}

int switchs(double a,double b,char s)
{
     switch (s)
	{
	case '+':
		{
			cls();
			printf("a+b\n");
            Sleep(500);
			printf("=%0.3lf+%0.3lf\n",a,b);
			Sleep(500);
			printf("=%0.3lf\n\007",a+b);
			Sleep(500);
		}break;
	case '-':
		{
			cls();
			printf("a-b\n");
			Sleep(500);
			printf("=%0.3lf-%0.3lf\n",a,b);
			Sleep(500);
			printf("=%0.3lf\n\007",a-b);
			Sleep(500);
		}break;
	case '*':
		{
			cls();
			printf("a*b\n");
			Sleep(500);
			printf("=%0.3lf*%0.3lf\n",a,b);
			Sleep(500);
			printf("=%0.3lf\n\007",a*b);
			Sleep(500);
		}break;
	case '/':
		{
			if(b==0)
			{
				cls();
				printf("³ýÊý²»ÄÜΪ0£¡\n\007");
				Sleep(500);
				goto R;
			}
			else
			{
				cls();
				printf("a/b\n");
				Sleep(500);
				printf("=%0.3lf/%0.3lf\n",a,b);
				Sleep(500);
				printf("=%0.5lf\n\007",a/b);
				Sleep(500);
			}
		}break;
		default: 
			{
				cls();
				printf("error!\n\007");
				Sleep(500);
				pause();
				cls();
				goto R;
			}
	}
R:;
}

int main(void)
{
        char c;
	double a,b;
	char s;
R:	printf("\007please input a formula:\n");
	scanf("%lf%c%lf",&a,&s,&b);
	if(a==0||b==0||s=='\0')printf("Error!");
	else switchs(a,b,s);
	pause();
	while((c = getchar()) != '\n' && c != EOF);
	a=0;b=0;s='\0';
	cls();
	goto R;
}