bin.c

#include <stdlib.h>
#include <stdio.h>

int main()
{
        int r[10];
        for(size_t i = 0; i < 10; i++) {
                r[i] = i + 1;
        }

        FILE* fp = fopen("a.dat", "wb");

        if(fp == NULL) {
                fprintf(stderr, "I/O error\n");
                return 1;
        }

        fwrite(r, sizeof(int), 10, fp);
        fclose(fp);

        return 0;
}