The Scope, Visibility, and Lifetime of Variables in C

• Scope of a Variable: The scope of a variable in C refers to the region of the program where the variable can be accessed. It defines where the variable is valid and can be used.
• Visibility of a Variable: Visibility determines whether a variable is accessible or hidden from other parts of the program. Variables can have local or global visibility based on their declaration.
• Lifetime of a Variable: The lifetime of a variable is the duration during which the variable exists in memory. It starts when the variable is declared and ends when it goes out of scope or the program terminates.
• Syntax:
  Local Variable:
  void functionName() {
  int localVar; // local variable
  // code
  }
  Global Variable:
  int globalVar; // global variable
  void main() {
  // code
  }
  Static Variable:
  void functionName() {
  static int staticVar; // static variable
  // code
  }
Program.c
#include <stdio.h> // Global variable with global scope int globalVar = 10; void myFunction() { // Local variable with local scope int localVar = 5; // Static variable with local scope static int staticVar = 20; printf("Local Variable: %d\n", localVar); printf("Global Variable: %d\n", globalVar); printf("Static Variable: %d\n", staticVar); } int main() { // Accessing global variable in the main function printf("Global Variable in main: %d\n", globalVar); // Calling a function that uses local, global, and static variables myFunction(); // Uncommenting the line below would result in a compilation error // printf("Local Variable outside function: %d\n", localVar); return 0; }

Output:
Global Variable in main: 10
Local Variable: 5
Global Variable: 10
Static Variable: 20