Answer 1

extern simply tells us that the variable is defined elsewhere and not within the same block where it is used.
Basically, the value is assigned to it in a different block and this can be overwritten/changed in a different block as well.
So an extern variable is nothing but a global variable initialized with a legal value where it is declared in order to be used elsewhere. It can be accessed within any function/block. Also, a normal global variable can me made extern as well by placing the ‘extern’ keyword before its declaration/definition in any function/block.
This basically signifies that we are not initializing a new variable but instead we are using/accessing the global variable only.
The main purpose of using extern variables is that they can be accessed between two different files which are part of a large program.