c++显示count未识别

int main()
{
    int i = 0;
    for (i = 100; i <= 200; i++)
    {
        int j = 0;
        for (j = 2; j < i; j++)
        {
            if(i%j==0)
            {
                break;
            }

        }
        if (j == i)
        {
            count++;
            printf("%d ", i);

        }
    }
    printf("\ncount = %d\n", count);
    return 0;
}

你之前没定义count，所以报错，而且你没加scanf的头文件

#include<iostream>
#include<stdio.h>
using namespace std;

int main()
{
    int i = 0,count;
    for (i = 100; i <= 200; i++)
    {
        int j = 0;
        for (j = 2; j < i; j++)
        {
            if(i%j==0)
            {
                break;
            }
        }
        if (j == i)
        {
            count++;
            printf("%d ", i);
        }
    }
    printf("\ncount = %d\n", count);
    return 0;
}

count没有声明，在函数开头添加一句
int count=0;