C language organization 1

// The Enumeration type is a constructor type that enables a group of Integer constants to list all possibilities for processing.
// Define enumeration use the enum keyword + name of the enumeration type {enumeration value, multiple enumeration values are separated by commas}; the last Semicolon is required.
// The enumerated type corresponds to a number that can be recognized by a person.
// If (condition expression) {statement} when the condition expression is true, execute the statement in braces. Otherwise, execute the statement after if.

// If (condition expression) {Statement 1} else {sentence 2}

Break; // end the current branch, jump out of the switch, and execute the following statement.
Default: // The execution sequence of the default statement is related to the position. If the corresponding branch is matched, the statement is executed.