What is storage class?

Question

In my 12th grade syllabus, there's a syntax for arrays
storage-class data-type array-name[expression]
Although, storage class is optional , but what it is?

Answer 1

Storage classes define how long a variable/array is available or in what parts of the program it's available from. See if this article helps you understand each class: https://www.programtopia.net/cplusplus/docs/storage-classes :D

I only understand the automatic, external, and register classes so I can't help with static or mutable, sorry.