How a bmp file bytes sorted as little endian, and gives me the first 2 bytes reverse?

Question

Everyone knows that BMP files are little-endian. The Wikipedia page says that the first 2 bytes must be 0x424D to make sure that this file is BMP, but when I am getting the first 2 bytes from a BMP file, it gives me the two bytes in reverse 0x4D42.

My code:

FILE *file;
unsigned short bmpidentifier;

if((file = fopen("c://loser.bmp", "rb")) == NULL){
   perror("The problem is");
   return -1;
}

fread(&bmpidentifier, sizeof(unsigned short), 1, file);
if(bmpidentifier == 0x424D){
   printf("The file actually is a bmp file.\n");
} else{
   printf("%X\n", bmpidentifier);
   printf("The file is not a bmp file.\n");
}

Now, how are the BMP file bytes sorted as little-endian, and giving me the first 2 bytes reversed?

Answer 1

The first byte is 'B' (0x42), the second byte is 'M' (0x4D)

A little endian uint16_t would see this as 0x4D42 which is what you are reading. Try the following instead for a endian independent solution.

char BM[3];
BM[2] = '\0';
if (fread(BM, 1, 2, file) && (strcmp("BM",BM)==0)) {
  printf("The file actually is a bmp file.\n");
}

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By the way Wiki says "ID field (42h, 4Dh)", not "first 2 bytes must be 0x424D".