# Keywords


https://en.cppreference.com/w/c/keyword


## Storage-class specifiers
* **auto**: automatic duration and no linkage

* **register**: automatic duration and no linkage; address of this variable cannot be taken

* **static**: static duration and internal linkage (unless at block scope) static duration and internal linkage, a function declared as static at the top level of a source file (outside any class definitions) – is only visible throughout that file ("file scope", also known as "internal linkage").
A variable declared as static at the top level of a source file (outside any function definitions) is only visible throughout that file

* **extern**: static duration and external linkage (unless already declared internal)

    Static storage and external linkage

If no storage-class specifier is provided, the defaults are:

* extern for all functions
* extern for objects at file scope
* auto for objects at block scope



## C Type qualifier

* **volatile**: disable optimization: within a single thread of execution, a volatile access cannot be optimized out or reordered relative to another visible side effect that is separated by a sequence point from the volatile access.
* **const**: Objects declared with const-qualified types may be placed in read-only memory by the compiler, and if the address of a const object is never taken in a program, it may not be stored at all.
* **restrict**: applies Only a pointer to an object type or an array thereof (since C23). Promotes optimization by 
retricting modification of memory through multiple pointers

## Other keyords

* inline: replace function call with its body for code optimization