int max (int x,int y);
return(x>y ? x:y);
main()
{
    int a,b;
    printf("input first number:");
    scanf("%d",&a);
    printf("input btcond number:");
    scanf("%d",&b);
    printf("max=%d\n",max(a,b));
}

int x=a,int y=b.  a>b?是的话输出a,否则输出b

#include<stdio.h>
int max (int x,int y)
 {    return(x>y ? x:y);
}
 main()
 {
     int a,b;
     printf("input first number:");
     scanf("%d",&a);
     printf("input btcond number:");
     scanf("%d",&b);
     printf("max=%d\n",max(a,b));
 }

敢问你怎么定义函数的？