What are the correct representation methods of C language constants?

What are the correct representation methods of C language constants

Numeric constants in C language can be simply divided into the following two types of integer constants And floating point number constants:

1. Integer constants such as 6, 27, -299

In C language, integer constants are divided into decimal integer constants, There are three representation forms: octal integer constant and hexadecimal integer constant.

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(1) Decimal integer constant

This kind of constant can only appear Numbers from 0 to 9, and can have positive or negative signs. For example:

0 1 364 28 -34

(2) Octal integer constant

This kind of constant is an octal number string starting with the number 0. The numbers are 0 to 7. For example:

0111（十进制 73） 011（十进制 9） 0123（十进制 83）

(3) Hexadecimal integer constant

This kind of constant is a hexadecimal number string starting with 0x or 0X. Each number can be a number or English letter from 0 to 9, a to f, or A to F. For example:

0x11（十进制 17） 0Xa5（十进制 165） 0x5a（十进制 90）

2. Floating-point constants such as 5.43, -2.3, 5.67f

Real-type constants have two representation forms: one is decimal form, The other is the exponential form.

(1) Decimal format

The decimal format is a decimal number string containing a decimal point.

This type of real constant can have no digits before or after the decimal point, but not at the same time. For example:

3.14159, .89, 56.0, 78., -3.0, 0.0

(2) Exponential form

The format of the exponential form consists of two parts: decimal fractional form or decimal integer constant part and exponent part.

The exponent part is e or E (equivalent to the base 10 of a power in mathematics) followed by an integer exponent (that is, a signed integer exponent). For example:

1e15 //表示数值 1×10
15
0.35e+1 //表示数值 0.35×10
1
78e-1 //表示数值 78×10
-1

The following is an incorrect real constant.

e15 //缺少十进制小数部分
0.35e //缺少阶码
78e-1.2 //不是整数阶码

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