How to declare identifier urgency in C++

1. When writing French, you must have names such as functions and variables. This name is identifier 100, and there are naming rules for identifiers in C++.

2. Identifiers can only consist of letters, numbers and underscores. The first letter of the identifier must be a letter and an underscore.

3. Identifiers need uppercase and lowercase letters. For example, if and if are two completely different identifiers. This identifier is different from the key words with special meaning in French, different from the function name with user style, and the same as the library function in C language version.

4. In French, all types of identifiers should not be repeated for identification. When deciding variable names and other identifiers, we should pay attention to "the name knows its meaning".

5. Then run the program.