Live-Demo - Globale Variablen

#include <iostream>

using namespace std;

int x = 10;

int main(void) {
    cout << x << endl;
    int x = 5;
    cout << x << endl;

    return 0;
}

compiler

Live-Demo - Speicherlayout

#include <iostream>

using namespace std;

int x = 10;         // global initialisiert
int y;              // global uninitialisiert

int main(void) {
    cout << x << endl;
    int x = 5;
    cout << x << endl;

    return 0;
}

Live-Demo - Seiteneffekte von globalen Variablen

#include <iostream>

using namespace std;

int x = 5;

void tuWas(void) {
    x *= x;
}

int main(void) {
    cout << x << endl;
    tuWas(); 
    tuWas(); 
    cout << x << endl;

    return 0;
}

compiler

Live-Demo - Variablenüberdeckung

#include <iostream>

using namespace std;

int main(void) {
    for (int i = 0; i < 3; i++) {
        for (int i = 0; i < 3; i++) {
            cout << i << " ";
        }
        cout << endl;
    }

	return 0;
}

compiler

Live-Demo - Statische lokale Variablen

#include <iostream>

using namespace std;

int count() {
    static int c{0};  // Wird nur beim ersten Mal aufgerufen
    int i = 3;
    i++;
    cout << "i = " << i << endl;
    return ++c;       // Statische Variable c wird mit jedem Aufruf erhöht.
}

int main() {
    for (int i{0}; i < 10; ++i) {
        int cnt = count();
        cout << "count() = " << cnt << endl;
    }
	return 0;
}

compiler

Live-Demo - Namensräume

#include <iostream>

using namespace std;

void print(int const n, double a[]) {
    for (int i = 0; i < n; i++) {
        cout << a[i];
        if (i != n - 1) cout << ",";
    }
    cout << endl;
}

void print(int n, double a[]) {
    while (--n >= 0) {
        cout << a[n] << " ";
    }
    cout << endl;
}

int main(void) {
    int constexpr n = 3;
    double a[n] = {1.1, 2.2, 3.3};

    print(n, a);

	return 0;
}

compiler