Join even and odd roms into one binary image.

bios_join.c

#include <stdio.h>

int main(const int argc, const char **args) {

  if (argc < 4) {
    printf("usage: %s even.bin odd.bin out.bin", args[0]);
    return 1;
  }

  FILE *odd = NULL;
  FILE *even = NULL;
  FILE *out = NULL;

  // open input files
  even = fopen(args[1], "rb");
  odd  = fopen(args[2], "rb");
  if (!even || !odd) {
    printf("unable to load bios halves");
    return 1;
  }

  // open output file
  out = fopen(args[3], "wb");
  if (!out) {
    printf("unable to open output file");
    return 1;
  }

  // while there are bytes to read
  while (!feof(even) && !feof(odd)) {

    unsigned char duo[2];

    // read 16bit byte pair
    if (!fread(duo + 0, 1, 1, even))
      break;
    if (!fread(duo + 1, 1, 1, odd))
      break;

    // write pair to output file
    fwrite(duo, 1, 2, out);
  }

  // close file handles
  fclose(even);
  fclose(odd);
  fclose(out);

  return 0;
}