100以内任意2个数的加法

#include<stdlib.h>
#include<stdio.h>
#include<math.h>

int main()
{
float a,b;
char op;
printf("enter your expression\n");
scanf("%f %c %f",&a,&op,&b);

switch(op)
{
case '+':printf("a%cb=%f\n",op,a+b);break;
case '-':printf("a%cb=%f\n",op,a-b);break;
case '*':printf("a%cb=%f\n",op,a*b);break;
case '/':printf("a%cb=%f\n",op,a/b);break;
default :printf("unknown operator\n");
}
system("pause");

}
四则运算！！！

#include<stdio.h>
#include<stdlib.h>
#include <time.h>

int add(int x,int y)
{printf("%d + %d =",x,y);
return x+y;}

void main()
{
printf("百以内加法运算：\n");
int n,x,y,z,result,sum=0;
srand((unsigned)time(NULL))