C language keywords, identifiers

First, the key word

C language provides a special meaning of the symbol, a total of 32, in Xcode all highlighted keywords, all the keywords are lowercase. such as return, int, and so on.

Second, identifiers

1. The variable name, function name, label, etc. used in the program are collectively called identifiers. Except for the function name of the library function, which is defined by the system, the rest is customized by the user. C Specifies that an identifier can only be a string of letters (A~Z,A~Z), Numbers (0~9), underscores (_), and that its first character must be a letter or an underscore.

2. The following points must also be noted when using identifiers:

(1) Standard C does not limit the length of identifiers, but it is limited by various versions of the C language compilation system, and is also limited by specific machines. For example, the first eight bits of the specified identifier are valid in a version C, and when the first eight bits of the two identifiers are the same, they are considered to be the same identifier.

(2) in identifiers, there is a difference in case capitalization. For example, book and book are two different identifiers.

(3) Although identifiers can be arbitrarily defined by programmers, identifiers are symbols used to identify a quantity. Therefore, the naming should try to have the corresponding meaning, in order to read comprehension, make "as the name implies".

C language keywords, identifiers