#include<stdio.h>
int main()
{
    int z=1,i,x;
    for(x=2;x<100;x++)
    {
        for(i=2;i<x;i++)
        {
            if (x%i==0)
            z=0;
            break;
        }
        if(z==1) printf("%d",x);
    }
    printf("\n");
    return 0;
}

23

--------------------------------
Process exited after 0.03071 seconds with return value 0
请按任意键继续. . .

z=1 明明只用于for中的子for，为什么要定义到for之外？很多错误都是自找的

#include <stdio.h>

int main( void )
{
    for( unsigned x=2; x<=100; ++x )
    {
        int z = 1;
        for( unsigned i=2; i<x; ++i )
        {
            if( x%i == 0 )
            {
                z = 0;
                break;
            }
        }
        if( z != 0 )
            printf( "%d\n", x );
    }
}

如果不用你本身的算法

#include <stdio.h>

int main( void )
{
    for( unsigned x=2; x<=100; ++x )
    {
        unsigned p = 1;
        for( unsigned i=2; p!=0 && i<x/i; ++i )
            p = x%i;

        if( p != 0 )
            printf( "%d\n", x );
    }
}

解释很详细，谢谢