Using some text editors to edit text file, you will see Add Unicode Signature (BOM) checkbox when open Save (As) File Dialogue with encoding UTF-8. So, what happend if you check (uncheck) this box?

The difference between 2 types!
I am using XVI32 to open 2 files, one is saved with Encoding UTF-8 and add BOM, other is saved without BOM.
The differences are 3 first bytes! UTF-8 BOM has EF BB BF chr(237) chr(187) chr(191)

Following is delBOM.c. (Dev-cpp)
#include <windows.h>
#include <stdio.h>

int main(int argn, char * argv[]) {
    FILE *fp;
   
    if (argn < 2) {
        MessageBox(0, “Where is second argument?”, “PVH”, 0);
        return 0;
    }
    int iFile;
for (iFile = 1; iFile < argn; iFile++) {
    fp = fopen(argv[iFile], “r”);
    if (!fp) {
        MessageBox(0, “Read file failed”, “PVH”, 0);
        continue;
    }
   
    char szString[65535];
    int nRead = fread(szString, sizeof(char), 65535, fp);
    //printf(“%d “, nRead);
    int iStart = 0;
    int iFinish = nRead;
    if(szString[0] == -17 && szString[1]==-69 && szString[2]==-65) {
        printf(“BOM will be removed”);
        iStart = 3;
    }
    rewind(fp);
    fclose(fp);
    if (iStart == 0) continue;
    fp = fopen(argv[iFile], “w+”); int i;
    for (i = iStart; i < iFinish; i++) {
        fputc(szString[i], fp);
    }
    fclose(fp);
}
    return 1;
}