A modifier is used to alter the meaning of the base type so that it more
precisely fits the needs of various situations.
* size
* sign

access modifier

• private
• public
• protected

qualifier

The type qualifiers provide additional information about the variables they precede.
* const
* volatile
* restrict

type specifier

• friend
• inline
• constexpr

storage specifier

format specifier

https://stackoverflow.com/questions/35218641/what-are-declarator-specifiers-in-c-language