C++ - SCOPE

Scope can be defined as the accessibility of a variable.

Say for example, in every office, there is a restricted area where only a few people have access.

Similarly, in C++, the variables also have some access restrictions. The variables that are defined inside a Function, cannot be accessed outside of it.

Example :

#include <iostream>
using namespace std;

void myFunction() {
	int x = 5;	
}

int main() {

    myFunction();
    cout << x;
    
    return 0;
}

Output :

error: 'x' was not declared in this scope

So, in the first line itself, the Function myFunction() is called.

myFunction();

And the function execution begins.

void myFunction()
{
	int x = 5;
}

And initialised the variable x with 5 inside the function fun().

int x = 5;

Then we come to the print statement,

cout << x;

And end up with an error as output,

Output :

error: 'x' was not declared in this scope

This is because the variable x is not accessable outside the Function. And that is called as Local Scope.

Local Scope

The variables that are declared inside a Function, can only be accessed inside the Function and is local to that Function. That is called the Local Scope of a variable.

Say for example, if there are two functions, firstFunction() and secondFunction().

Example :

#include <iostream>
using namespace std;

void firstFunction() {
	int x = 5;
	cout << "The variable x : " << x << " is not accesible outside the firstFunction()" << endl;
}	
	
void secondFunction() {
	int y = 7;
	cout << "The variable y : " << y << " is not accesible outside the secondFunction()" << endl;
}

int main() {

    firstFunction();
	secondFunction();
	
	return 0;
}

Output :

The variable x : 5 is not accesible outside the firstFunction()
The variable y : 7 is not accesible outside the secondFunction()

So, we have declared two functions, firstFunction(),

void firstFunction()
{
	int x = 5;
	cout << "The variable x : "+x+" is not accesible outside the firstFunction()";
}

And secondFunction().

void secondFunction()
{
	int y = 7;
	cout << "The variable y : "+y+" is not accesible outside the secondFunction()";
}

And we have two variables, x and y.

While x is declared inside the Function firstFunction() and is local to the firstFunction() and cannot be accessed outside it.

Similarly, y is declared inside the Function secondFunction() and is local to the secondFunction() and cannot be accessed outside it.

Next, let us see the Local Scope in nested Function.

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