向文件写入127个ASCLL码，这程序是什么回事不行

# include <stdio.h>
int main()
{
char a=0;
FILE *fp;
errno_t x;
if ((x = fopen_s(&fp, "E:\\写入.txt", "wb")) == 0)
printf("the file was opened!\n");
else
printf("the file was not opened!\n");
for (; a < 128; a++)
fputc(a, fp);
fclose(fp);
}