#include <stdio.h>
int main(void)
{
    int a,b,c;
    char x;
    fprintf(stdout,"求两个数的运算\n");
    fscanf(stdin,"%d%c%d",&a,&x,&b);
    if  (x=="-")
    {
    c=a-b;
    fprintf(stdout,"结果是%d\n",c);
    }
     else if   (x=="+")
    {
    c=a+b;
fprintf(stdout,"结果是%d\n",c);
    }
    else
    {
    fprintf(stdout,"error!\n");
    }
    return 0;


}

#include <stdio.h>
int main(void)
{
    int a,b,c;
    char x;
    printf("求两个数的运算\n");
    scanf("%d%c%d",&a,&x,&b);
    if  (x=='-')
    {
    c=a-b;
    printf("结果是%d\n",c);
    }
     else if   (x=='+')
    {
    c=a+b;
    printf("结果是%d\n",c);
    }
    else
    {
    printf("error!\n");
    }
    return 0;


} 

正确啊，我试了