You can enter bit patterns into the binary-hex-decimal ready reckoner on the right and it will instantly convert from the number you are entering into the other two bases.

The convention in C is to tell the compiler a number is hexadecimal by putting the characters 0x before the number. Remember that if I want to combine and manipulate bit patterns I can use the set of C logical operators, OR, AND and XOR, to help me do this.