Integers can be expressed in several bases:
Decimal. Decimal integers begin with a non-zero digit followed by zero or more decimal digits (0–9).
Binary. Binary integers begin with “0b” or “0B” followed by zero or more binary digits (0, 1).
Octal. Octal integers begin with zero (0) followed by zero or more octal digits (0–7).
Hexadecimal. Hexadecimal integers begin with “0x” or “0X” followed by one or more hexadecimal digits (0–9, A–F). Hexadecimal digits can be either uppercase or lowercase.