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

void main()
{
    int i,j,k,n=0;
    for(i=0;i<=100;i++)
    {        
        if(i=2)
        {
            n++;
            if(n%5==0) printf("\n");
            printf("%d\t",i);
        }        
        else
        {
            k=(int) sqrt(i*1.0);
            for(j=2;j<=k;j++)
            {
                if(i%j==0) break;
            }
            if(j>=k+1)
            {
                n++;
                if(n%5==0) printf("\n");
                printf("%d\t",i);
            }
        }
    }

}      要求求0-100的质数，一行输出5个

把两个输出和换行调换一下，就可以一行5个了，毕竟是先输出，才换行嘛；
其次，是i==2，不是i=2;!!!

谢谢，确实是该==2，疏忽了

#include <stdio.h>
int main()
{
    int i,j,k,n=0;
    for(i=2;i<=100;i++)
        {k=1;
        if(i==2)
        {
        n++;
        printf("%d\t",i);
        continue;
        }
        for(j=2;j<i;j++)
            {
            if(i%j==0)
            k=0;
            break;
            }
            if(k==1)
            {
            n++;
            printf("%d\t",i);
            }
            if(n%5==0)
            printf("\n");
        }
            return 0;
}