1、计算两个数的和差积商

#include
     
      int add(int x,int y){        return(x+y);}int minus(int x,int y){    return(x-y);}int multip(int x,int y){    return(x*y);}float mod(float x,float y){    return(x/y);}int main(){    int add(int x,int y);    int minus(int x,int y);    int multip(int x,int y);    float mod(float x,float y);    int a,b;    printf("Input two numbers:");    scanf("%d,%d",&a,&b);    printf("和=%d\n",add(a,b));    printf("差=%d\n",minus(a,b));    printf("积=%d\n",multip(a,b));    printf("商=%f\n",mod((float)(a),(float)(b)));    return 0;}
     

 

2、编写函数，判断是否为素数

#include
     
      #include
      
       int main(){    int prime(int x);    int a,b;    printf("Input a number:\n");    scanf("%d",&a);    b=prime(a);    if(b)        printf("%d is a prime\n",a);    else        printf("%d isn't a prime\n",a);    return 0;}int prime(int x){    int i,n=1;    for(i=2;i<=sqrt(x);i++)    {        if(x%i==0)        {n=0;break;}    }    return (n);}
      
     

 

3、找出最大数

#include
     
      int main(){    int max2(int x,int y);    int max4(int p,int q,int s,int t);    int a,b,c,d;    printf("Input four numbers:\n");    scanf("%d,%d,%d,%d",&a,&b,&c,&d);    printf("max=%d\n",max4(a,b,c,d));    return 0;}int max2(int x,int y){    return ((x>y)?x:y);}int max4(int p,int q,int s,int t){    int max2(int x,int y);    int a,b;    a=max2(p,q);    b=max2(s,t);    return(max2(a,b));}