C Programming - Declarations and Initializations - Discussion

Global variable declaration is we can access to any of the function or files.

Want to know more details down to follow here.

First up all we want to know about data types or storage class.

There are 4 classes.

1. Local variable.
2. Static variable.
3. Global variable.
4. Register variable.

Local variable only to use a function. We cannot access other function and life is a function only.

Static variable is one or more function to use, the static variable is update automatically.

Global variable is declaration the variable is out side the function, so we can use the variable in any of the function.

Register variable declaration only internal the CPU memory.

Without extern keyword we can not access the variable with in outside file to another file.

Yes, we need to declare a extern keyword variable in other files of program where we want to use it.

If the sub functions f1 and f2 share the function f1 datatypes, no need to specify again the datatypes, otherwise we have to mention extern.

because only extern variables can be used in more than one file and to inform the compiler that these are declare some other file it needs to specify the keyword extern,

We can able to call the file by using extern keyword only because the file is external file.

We have to declare extern keyword otherwise we have to define the variable 'a' with in each function or else we have to declare 'a' as a global variable.

How to include F1 file's variable in the other Files... With syntax... thanks

Yes we have to declare extern keyword otherwise we have to define the variable 'a' with in the function. Without declaration of extern keyword and define the variale if we compile we will get linked error.

Here, we have to declare variable globally. So both f2 & f3 can use that varible.