volatile const

"volatile const" is a combination of two keywords in C/C++ that can be used to declare a variable.

The "const" keyword is used to declare a variable as read-only, meaning it cannot be modified after it has been initialized.

The "volatile" keyword is used to indicate that the value of the variable may change at any time, even if it doesn't appear to be modified in the code. This is often used for variables that are shared between multiple threads or that are directly mapped to hardware registers.

The combination of "volatile const" indicates that the variable is both read-only and its value may change at any time. This is typically used for variables that are memory-mapped to hardware registers and need to be treated as constants in the code, but whose values may change due to external factors.