CODEWITHSUNDEEP
c++scope
KNFZ
KNFZ

Reputation: 33

Global and local variables in C++

I'm fairly new to C++, and I'm experiencing some issues when printing local and global variables. Consider this simple piece of code:

#include <cstdlib>
#include <iostream>

using namespace std;

/*
 * 
 */
int x = 10; // This x is global
int main() {
    int n;
    { // The pair of braces introduces a scope  
    int m = 10;    // The variable m is only accessible within the scope
    cout << m << "\n";

    int x = 25; // This local variable x hides the global x
    int y = ::x; // y = 10, ::x refers to the global variable x
    cout << "Global: " << y << "\n" << "Local: " << x << "\n";
    {
        int z = x; // z = 25; x is taken from the previous scope
        int x = 28; // it hides local variable x = 25 above
        int t = ::x; // t = 10, ::x refers to the global variable x
        cout << "(in scope, before assignment) t = " << t << "\n";
        t = x; // t = 38, treated as a local variableout was not declared in this scope
        cout << "This is another hidden scope! \n";
        cout << "z = " << z << "\n";
        cout << "x = " << x << "\n";
        cout << "(in scope, after re assignment) t = " << t << "\n";
    } 
    int z = x; // z = 25, has the same scope as y
    cout << "Same scope of y. Look at code! z = " << z;
    }
    //i = m; // Gives an error, since m is only accessible WITHIN the scope

    int m = 20; // This is OK, since it defines a NEW VARIABLE m
    cout << m;

    return 0;
}

My goal is practicing the accessibility of the variables within the various scopes, and then printing them. However, I'm not able to figure out why when I try to print the last variable z, NetBeans gives me back the output 2025. Here it follows my sample output:

10
Global: 10
Local: 25
(in scope, before assignment) t = 10
This is another hidden scope! 
z = 25
x = 28
(in scope, after re assignment) t = 28
Same scope of y. Look at code! z = 2520
RUN FINISHED; exit value 0; real time: 0ms; user: 0ms; system: 0ms

Hope that somebody can help me understanding what is going on! :)

Upvotes: 3

Views: 226

Answers (1)

ΦXocę 웃 Пepe&#250;pa ツ
ΦXocę 웃 Пepe&#250;pa ツ

Reputation: 48258

is not that z is holding the value 2520 is the fact that you ommit to add a new line operator between printing z and printing m...

you are doing:

cout << "Same scope of y. Look at code! z = " << z;
}

int m = 20;  
cout << m;

but you should do:

std::cout << "Same scope of y. Look at code! z = " << z << std::endl;
}

int m = 20;  
std::cout << m << std::endl;

if you just followed the same criteria of labeling the output and doing something like

std::cout << "M is: "<<m << std::endl;

you would spotted the issue faster by observing the output:

25M is: 20

Upvotes: 4

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