Why use hex?

Question

Hey! I was looking at this code at http://www.gnu.org/software/m68hc11/examples/primes_8c-source.html

I noticed that in some situations they used hex numbers, like i

Answer 1

To be more precise, hex and decimal, are all NUMBERS. The radix (base 10, 16, etc) are ways to present those numbers in a manner that is either clearer, or more convenient.

When discussing "how many of something there are" we normally use decimal. When we are looking at addresses or bit patterns on computers, hex is usually preferred, because often the meaning of individual bytes might be important.

Hex, (and octal) have the property that they are powers of two, so they map groupings of bit nicely. Hex maps 4 bits to one hex nibble (0-F), so a byte is stored in two nibbles (00-FF). Octal was popular on Digital Equipment (DEC) and other older machines, but one octal digit maps to three bits, so it doesn't cross byte boundaries as nicely.

Overall, the choice of radix is a way to make your programming easier - use the one that matches the domain best.