Latex three standard text book, report, article chapter commands and level depth

Latex has three standard text categories: Book, report, article. The chapter commands and hierarchy depth for each type of text are as follows:

Chapter commands and level depth of three standard text classes

Level depth	Hierarchy name	Book	Report	Article
-1	Part	\part	\part
0	Chapter	\chapter	\chapter	\part
1	Section	\section	\section	\section
2	Subsection	\subsection	\subsection	\subsection
3	Subsubsection	\subsubsection	\subsubsection	\subsubsection
4	Paragraph	\paragraph	\paragraph	\paragraph
5	Subparagraph	\subparagraph	\subparagraph	\subparagraph

This digest is from the Handbook of Complete Latex Studies (second edition, Hu Wei)

Latex three standard text book, report, article chapter commands and level depth