Difference Between Local and Global Variable


In this post, we will understand the difference between local and global variables.

Local variable

  • It is generally declared inside a function.

  • If it isn’t initialized, a garbage value is stored inside it.

  • It is created when the function begins its execution.

  • It is lost when the function is terminated.

  • Data sharing is not possible since the local variable/data can be accessed by a single function.

  • Parameters need to be passed to local variables so that they can access the value in the function.

  • It is stored on a stack, unless mentioned otherwise.

  • They can be accessed using statement inside the function where they are declared.

  • When the changes are made to local variable in a function, the changes are not reflected in the other function.

  • Local variables can be accessed with the help of statements, inside a function in which they are declared.

Example

Following is an example −

#include <stdio.h>
int main () {
   /* local variable declaration */
   int a, b;
   int c;
   /* actual initialization */
   a = 10;
   b = 20;
   c = a + b;
   printf ("value of a = %d, b = %d and c = %d
", a, b, c);    return 0; }

Global variable

  • It is declared outside the function.

  • If it isn’t initialized, the value of zero is stored in it as default.

  • It is created before the global execution of the program.

  • It is lost when the program terminates.

  • Data sharing is possible since multiple functions can access the global variable.

  • They are visible throughout the program, hence passing parameters is not required.

  • It can be accessed using any statement within the program.

  • It is stored on a specific location inside the program, which is decided by the compiler.

  • When changes are made to the global variable in one function, these changes are reflected in the other parts of the program as well.

Example

Following is an example −

#include
/* global variable declaration */
int g;
int main () {
   /* local variable declaration */
   int a, b;
   /* actual initialization */
   a = 10;
   b = 20;
   g = a + b;
   printf ("value of a = %d, b = %d and g = %d
", a, b, g);    return 0; }

Updated on: 24-Mar-2021

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