Quote:

#include <stdio.h>
#include <stdlib.h>
int sum(int n)
{
int k=0;
if(n==1)return 1;
k=n+sum(n-1);
return k;
}
void main(int argc,char *argv[])
{
int n;
FILE *fp;
if(argc!=2)
{
  printf("\nToo few parameter");
  exit(0);
} printf("\nEnter a integer number:(>0)");
scanf("%d",&n);
fp=fopen(argv[1],"w");
printf("sum(n)=%d",sum(n));
fprintf(fp,"sum(n)=%d",sum(n));
fclose(fp);
}