1. In computer science, the word hexadecimal means base-16 numbers. These are numbers that use digits in the range: 0123456789ABCDEF. In the C programming language (as well as Java, JavaScript, C++, and other places), hexadecimal numbers are prefixed by a 0x. In this manner, one can tell that the number 0x80 is equivalent to 128 decimal, not 80 decimal. Key point: Hex is so important because 4-bits have 16-possible combinations. Therefore, a 4-bit value can be represented by a single hex digit. In this manner, every byte (8-bits) can be represented by two hex digits. Key point: Script kiddies tend to dismiss hexadecimal as one of those "unnecessary details". In reality, you must be able to comfortably do hex math in your head, and freely convert with binary. You should also be able to interpret hexdumps, where a block of data is dumped out into columns of hex numbers. A tutorial for this is at http://www.robertgraham.com/pubs/sniffing-faq.html#hexadecimal. Key point: My mother, an otherwise avowed computerphobe, calculates her age in hex. She is in her early 0x30s. (For those who cannot do the math as well as my mom, 0x30 == 3*16 == 48). From Hacking-Lexicon