Hi,

I'm currently writing a program that will command a peripheral device by receiving a sentence. In order for it to interpret the sentence it must end with two hexadecimal checksum charaters . The checksum is the hexadecimal representation of the exclusive-or of all the remaining characters in the sentence.

At the moment i'm exclusive ORing the remaining characters in the sentence, however, this only gives me a result of one character, i'm unsure what to do. Any guidance would be appreciated.

Regards,
Andrew

One byte consists of eight bits, which contains two hexadecimal digits.

Regards,

Dave

One byte consists of atleast eight bits.

Well, the C and C++ standards say that a char is at least eight bits (they don't talk about bytes). I think the term "byte" originated at IBM a little after the middle of the 20th century. By the time it got into common usage (with the release of the IBM 360, as I recall) it designated an eight-bit quantity. Non-IBM (maybe anti-IBM) people are persnickety about referring to "octets" instead of bytes, and maybe I should have used that term. (But would it have been more clear to the Original Poster? By the same token, instead of hexadecimal digit I could have used the term "semioctet" for the 4-bit thingie that is half of an octet. Some people used to call them "nybbles". Really.)

I assume that a byte is always eight bits and has been since about 1964, and it is so commonly used that way that I didn't feel it necessary to define it in-line. Sometimes I think my posts are too wordy anyhow. No, really!

Maybe I was a little lax in not defining the terminology, and the fact that the statement that I made is (almost certainly) correct in the context of any computer system that the Original Poster is likely to run across these days is not an excuse for not being more precise. Sometimes I need a little help.

(DId I just say "almost certainly correct"? That just doesn't sound right, does it? If it's not always correct, it's not correct. Period.)

Thanks for posting.

Regards,

Dave

Or a nybble

Believe it or not, I had just edited my post to include that term, but I was working from memory, not Wikipedia. Really. (Note that my last edit was submitted at precisely the same time as your post.) I think it's about time for one of us to sign off for now. I vote for me.

Regards,

Dave