Заполнить массив числами Фибоначчи и записать в файл

#include <iostream>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
 
int main()
{
    FILE *f;  int i=0,n=10;
     if (!(f = fopen ("input.txt", "rb"))) {cout << "\nFileError"; return 0;}
     fscanf(f,"%d",&n);
     fclose(f);
     if (!(f = fopen ("output.txt", "wb"))) {cout << "\nFileError"; return 0;}
unsigned long int *buf= (unsigned long int*)malloc((n+1)*sizeof(unsigned long int));
    buf[0]=0;
    buf[1]=1;
    for (i=1;i<=n+1;i++)
        {
        buf[i+1]=buf[i]+buf[i-1];
        fprintf(f,"%d\n",buf[i-1]);
        }
    fclose(f);
    return 0;
}

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
 
#define INPUT_FILENAME "input.txt"
#define OUTPUT_FILENAME "output.txt"
 
int main()
{
    FILE *f;
    int* a;
    int n, i;
 
    if ((f = fopen(INPUT_FILENAME, "r")) == NULL) {
        printf("\nError. Can't open file %s.", INPUT_FILENAME);
        exit(1);
    }
    fscanf(f, "%d", &n);
    fclose(f);
 
    if ((f = fopen(OUTPUT_FILENAME, "w")) == NULL) {
        printf("\nError. Can't open file %s.", OUTPUT_FILENAME);
        exit(1);
    }
 
    a = new int [n];
 
    a[0] = 1;
    a[1] = 1;
 
    fprintf(f, "%d ", a[0]);
    fprintf(f, "%d ", a[1]);
 
    for (i = 2; i < n; i++)
    {
        a[i] = a[i-1] + a[i-2];
        fprintf(f, "%d ", a[i]);
    }
 
    fclose(f);
 
    _getch();
    return 0;
}

unsigned long int *buf= (unsigned long int*)malloc((n+1)*sizeof(unsigned long int));

a = new int [n];

unsigned int *s=malloc(n*2);

a = 0;
b = 1;
for .... {
   printf("%ld\n", b);
   t = b;
   b += a;
   a = t;
}