Function in C Part 3:Scope of Variables:

 

Scope of Variables:

• A scope is a region of the program, and the scope of variables refers to the area of the program where the variables can be accessed after its declaration.

• The scope of the variable is simply lifetime of a variable. It is block of code under which a variable is applicable or alive. 

• There are three places where variables you can declare variable programming language:

1. Inside a function or a block: Local variables

2. Outside of all functions: Global variables

3. In the definition of function parameters: Formal parameters

Local Variables:

• Variables that are declared inside a function or block are called local variables. 

• The local variables exist only inside the block in which it is declared.

• The local variable exists until the block of the function is under execution. After that, it will be destroyed automatically.

• Example of  Local Variable 

public int add(){ 

int a =4; 

int b=5; 

return a+b; 

} 

Here, 'a' and 'b' are local variables

#include<stdio.h>

int main()

{

    int a = 100;

    {

        int a = 10;  

        printf("Inner a = %d\n", a);

    }

    printf("Outer a = %d\n", a);

    return 0;

}

Output:

Inner a = 10

Outer a = 100

Global Variables :

• Global variables are defined outside a function, usually on top of the program (Global declaration section).

• It has a global scope means it holds its value throughout the lifetime of the program.

• Any function can access and modify global variables. That is, a global variable is available for use throughout your entire program after its declaration. 

• Global variables are automatically initialized to 0 at the time of declaration. 

• Example:

int a =4; int b=5; 

public int add()

{ 

return a+b;

 }

 Here, 'a' and 'b' are global variables.

#include<stdio.h>

void func_1();

void func_2();

int a, b = 10;  // declaring and initializing global variables

int main()

{

    printf("Global a = %d\n", a);

    printf("Global b = %d\n\n", b);

    func_1();

    func_2();

    return 0;

}

void func_1()

{

    printf("From func_1() Global a = %d\n", a);

    printf("From func_1() Global b = %d\n\n", b);

}

void func_2()

{

    int a = 5;

    printf("Inside func_2() a = %d\n", a);

}

Output:

Global a = 0

Global b = 10

From func_1() Global a = 0

From func_1() Global b = 10

Inside func_2() a = 5