In C language, integer constants can be expressed in decimal, octal and hexadecimal.

Decimal integer constant: can only appear.

0~9

Numbers, and can be signed. take for example

1 1

Octal integer constant: in numbers

Octal digit string at the beginning, where the number is

0~7。 take for example

0 1 1 (decimal 9)

Hexadecimal integer constant: in

0x

or

0x

Hexadecimal digit string at the beginning, where each digit can be

0~9、a~f

or

a~

f

Numbers or English letters. take for example

0x 1 1 (decimal

17)