Как объединить 2 файла в один (третий) на чистом Си? - C (СИ)

#define _CRT_SECURE_NO_WARNINGS
 
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
 
int main(void)
{
    FILE *origin = NULL;
    FILE *second_origin = NULL;
    FILE *output = NULL;
    char current_symbol;
 
    if (!(origin = fopen("input1.txt", "r")))
       {
            printf("Here is the error while opening the first file!");
            exit(1);
       }
    if (!(second_origin = fopen("input2.txt","r")))
    {
        printf("Here is the error while opening the second file!");
        exit(2);
    }
    if (!(output = fopen("output.txt","w")))
    {
        printf("Here is the error while opening the output file!");
        exit(3);
    }
 
 
    while (!feof(origin))
    {
        current_symbol = fgetc(origin);
        if (current_symbol == EOF)
            break;
        fprintf(output, "%c", current_symbol);
    }
    
 
    fprintf(output, "\n");
 
    while (!feof(second_origin))
    {
        current_symbol = fgetc(second_origin);
        if (current_symbol == EOF)
            break;
        fprintf(output, "%c", current_symbol);
    }
    fclose(origin);
    fclose(output);
        fclose(second_origin);
}