C/C++ Why to use unsigned char for binary data?

Question

Is it really necessary to use unsigned char to hold binary data as in some libraries which work on character encoding or binary buffers? To make sense of my que

Answer 1

You'll get most of your problems when comparing the contents of individual bytes:

char c[5];
c[0] = 0xff;
/*blah blah*/
if (c[0] == 0xff)
{
    printf("good\n");
}
else
{
    printf("bad\n");
}

can print "bad", because, depending on your compiler, c[0] will be sign extended to -1, which is not any way the same as 0xff