/** This program illustrates the difference between local and global variables, their scope and how their priority and how they are accessed during the execution of a program. */ /** Additional comments can be found at the end of the code. * HAPPY LEARNING! */ /*************** CODE ************************/ #include using namespace std; int i = 1; // global variable void firstFunction(); void secondFunction(); void thirdFunction(); int main() { int i = 2; // local variable to main() cout << "Inside main(): i=" << i << endl; /* see 1 */ firstFunction(); secondFunction(); thirdFunction(); return 0; } void firstFunction(){ int i = 3; // local variable to firstFunction() cout << "Inside firstFunction(): i=" << i << endl; /* see 2 */ } void secondFunction(){ cout << "Inside secondFunction(): i=" << i << endl;/* see 3 */ } void thirdFunction(){ int i = 4; // local variable to thirdFunction() cout << "Inside thirdFunction(): i=" << ::i << endl; /* see 4 */ } /*************** COMMENTS ********************/ /* 1. At this point in the program there are two visible variables, (global i=1) and (local i= 2) When this statement is executed the local variable is printed since it has priority over the global variable. */ /* 2 Similar to the main() example, the local variable i=3 is selected for printing.*/ /* 3. There is no local variable i in this function, therefore the global variable i=1 will be printed.*/ /* see 4 Even though there is a local variable i=4 in this function, the value of the global variable i=1 is printed. This is because we are here using the scope resolution operator (::) which forces the program to use the available global variable. */

Variable Scope - Local vs. Global - Example