What are legal constants in C language?

In C language, legal constants must: have a clear type: integer, floating point number, or character. Value is valid: within type range. No side effects: the value does not depend on program execution. Representations include: integers, floating point, characters, string constants, and escape sequences.

What are legal constants in C language?

In C language, constants refer to values ​​that remain unchanged while the program is running. Unlike variables, constants cannot be reassigned after they are defined.

Legitimate C language constants must meet the following requirements:

• Clear type: Constants must have a clear data type, such as integer, floating point number, or character.
• Value is valid: The value of a constant must be within the range allowed by the type.
• No side effects: The value of a constant cannot depend on the execution of other parts of the program.

• Representation form: Constants can use the following representation forms:

  • Integer constants: In decimal, octal Or an integer represented in hexadecimal, such as 10, 074, or 0xFF.
  • Floating point constant: Floating point number with decimal point, such as 3.14 or 0.0001.
  • Character constants: A single character enclosed in single quotes, such as 'a' or '?'.
  • String constant: A series of characters enclosed in double quotes, such as "Hello World!".
  • Escape sequence: A special character sequence that represents non-printable characters or other special characters, such as '\n' (newline) or '\t' (tab) .

For example, the following are some legal C language constants:

<code class="c">int my_age = 25; // 整型常量
float pi = 3.14; // 浮点常量
char letter = 'A'; // 字符常量
const char* greeting = "Hello World!"; // 字符串常量</code>

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