Story about Macro

1.The macro contains special symbols

1.1 String operator（#）

1.2 Symbolic join operator（##）

1.3 Continuation operator（\）

2.do{...}while(0)

2.1 Avoid semantic misinterpretation

2.2 Avoid using goto to control flow

2.3 Avoid warnings caused by macros

2.4 Define a single function block to perform complex operations