Data Type C++

Storage classes define the scope and lifetime of the variable and function within a C program.

Types of Storage Classes in C++

1. Auto
2. Register
3. Static
4. Extern

1. Auto Storage Class:- This is the default storage class for local variables.
For example:

 {
int num;
auto int month; 
 }

2. Register Storage Class:-This is used to define the local variable that should be stored in register instead of RAM.
For example.

 {
 register int miles; 
 }

3. Static Storage Class:-This is the default storage class for global variables.
For example:

{
int num;
static int count;
main()
cout<<count;
}

4. Extern Storage Class:- Extern is use to give a reference of global variable that is visible to all the program files.
For example:

//File 1: main.cpp
#include <iostream>
#include <conio.h>
int count ;
extern void write_extern();
main()
{
count = 5;
write_extern();
} 

//File 2: write.cpp
#include <iostream>
#include <conio.h>
extern int count;
void write_extern(void)
{
std::cout << "Count is " << count << std::endl;
} 

Note:-Here extern keyword is being used to declare count in another file.