很多循环语句都可以做的
#include "stdio.h"
void main()
{
    int i,N,S;
    i=0;
    S=0;
         printf("Please into a number N:");
    scanf("%d",&N);
    while(i<=N)
    {
        S=S+i;
        i++;
    }
    printf("The end number is:%d",S);
        
   
}
再说个，
void main()
{
    int i,N,s=0;
    printf("Please into a number N:");
    scanf("%d",&N);
    for(i=1;i<=N;i++)
       {
             s=s+i;
       }
     printf("The end number is:%d",s);
}

main()
{int n,i;
for(i=1,i<=n,i++) s=s+i
printf("s=%d",s);}

#include<stdio.H>
void main()
{
    int a,b,sum;
    sum=0;b=1;
    scanf("%d",&a);
    while(b<=a)
    {
        sum=b+sum;
        b++;
    }
    printf("%d\n",sum);
}
再发一次

不错。这个都会写了。。继续加油

lz应该是想了解循环的用法，所以N*(N+1)/2这种数学技巧可能并没有回答道lz的问题,那么用循环的话：

int total = 0;
for( int iter = 1; iter <= N; ++iter ) {
 total += iter;
}

// you can print total like this
printf("total is: %d\n", total);