Learn Variable Scopes | Introduction

Variable scope refers to the region or context within a program where a particular variable is visible and accessible. In other words, it defines where you can use a variable in your code and determines its lifetime.

Variables declared within a function have local scope. They are accessible only within the function or the block of code inside which they were declared. Local variables are created when the program enters the block where they are defined and destroyed when the block is exited.

Note

A code block is a set of statements enclosed within curly braces { }.

main.cpp


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#include <iostream>

int example()
{
	// Create variable inside the function
    int local = 10;
    return local;
}

int main()
{
	// Try to access the variable created inside function
    std::cout << local;
}

The error error: ‘localVar’ was not declared in this scope appears because localVar exists only inside MyFunction() and is destroyed after it ends. To access its value, return it from the function and store it in a variable inside main().

main.cpp


              123456789101112131415
            
#include <iostream>

int example()
{
	// Create variable inside the function
    int local = 10;
    return local;
}

int main()
{
	// Assign the result of the function to a new variable
	int result = example();
    std::cout << result << std::endl;
}

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Section 1. Chapter 4

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Note

A code block is a set of statements enclosed within curly braces { }.

main.cpp


              1234567891011121314
            
#include <iostream>

int example()
{
	// Create variable inside the function
    int local = 10;
    return local;
}

int main()
{
	// Try to access the variable created inside function
    std::cout << local;
}

main.cpp


              123456789101112131415
            
#include <iostream>

int example()
{
	// Create variable inside the function
    int local = 10;
    return local;
}

int main()
{
	// Assign the result of the function to a new variable
	int result = example();
    std::cout << result << std::endl;
}

Everything was clear?

Thanks for your feedback!

Section 1. Chapter 4