留念 C语言第一课简单的计算器制作

#include<conio.h>
void displayMenu();
void add();
void sub();
void multiply();
void divide();
void yushu();
void jiecheng();
void leijia();
void jiechengleijia();
int main(int n)
{do
{system("color 2e");
system("cls");
displayMenu();
system("pause");}
while(n);}
int n;
void displayMenu()
{ printf("***welcome to use simple calculator***\n");
printf("the author is xiaobo\n");
printf("No.1 add\n");
printf("No.2 sub\n");
printf("No.3 multiply\n");
printf("No.4 divide\n");
printf("No.5 yushu\n");
printf("No.6 jiecheng\n");
printf("No.7 liejia\n");
printf("No.8 jiechengleijia\n");
printf("No.0 exit\n");
scanf("%d",&n);
switch(n)
{ case 1:add(); break;
case 2:sub(); break;
case 3:multiply(); break;
case 4:divide(); break;
case 5:yushu(); break;
case 6:jiecheng(); break;
case 7:leijia(); break;
case 8:jiechengleijia();break;
case 0:exit(0);return;}
}
void add()
{ double num1,num2;
double sum;
printf("Please Input 2 numbers to add\n");
scanf("%lg%lg",&num1,&num2);
sum =num1+num2;
printf("sum is %lg\n",sum);}
void sub()
{ double num1,num2;
double sum;
printf("Please Input 2 numbers to sub\n");
scanf("%lg%lg",&num1,&num2);
sum =num1-num2;
printf("the result is %lg\n",sum);}


void multiply()
{ double num1,num2;
double sum;
printf("Please Input 2 numbers to multiply\n");
scanf("%lg%lg",&num1,&num2);
sum =num1*num2;
printf("the result is %lg\n",sum);}
void divide()
{ double num1,num2;
double sum;
printf("Please Input 2 numbers to divide\n");
scanf("%lg%lg",&num1,&num2);
sum =num1/num2;
printf("the result is %lg\n",sum);}

//http://www.cnblogs.com/xiaobo-Linux/ QQ463431476
void yushu()
{int num1,num2;
int sum;
printf("please Input 2 numbers for yushu\n");
scanf("%ld",&num1,&num2);
sum =num1%num2;
printf("yushu is %ld\n",sum);
}
void jiecheng()

{double i,j=1;
double sum=1;
printf("Please Input a integer number for jiecheng\n");
scanf("%lg",&i);
for(;j<i;j++)
{sum *=j;}
sum *=i;
printf("the result is %lg\n",sum);}
void leijia()
{double n;
double sum=0;
printf("please input any number more than 0, with less than 0 number to end\n");
for(n=0;n>=0;)
{sum +=n;
scanf("%lg",&n);}
printf("the result is %lg\n",sum); }
void jiechengleijia()
{ int i,a[5];
long j,k=1,sum=0;
printf("please input any 5 integer numbers\n");
for(i=0;i<5;i++)
{scanf("%d",&a[i]);
for(j=a[i];j>=1;j--)
{k =k*j;}
sum +=k;
k=1;}
printf("\nthe sum is %ld\n",sum); }
/* 2014 /12. 25 做 */