Code 1

#include<iostream>
using namespace std;

int main(){
    int n;
    cout<<"Enter the rows for Cube: ";
    cin>>n;
    for (int i=0;i<n;i++){
        for (int j=0;j<n;j++){
            cout<<"* ";
        }
        cout<<endl;
    }
    return 0;
}

Output

Enter the rows for Cube: 4

* * * *
* * * *
* * * *
* * * *

Code 2

#include<iostream>
using namespace std;

int main(){
    int n;
    cout<<"Enter the rows for Cube: ";
    cin>>n;
    Cout<<"Enter the symbol or character: ";
    string x;
    cin>>x;
    for (int i=0;i<n;i++){
        for (int j=0;j<n;j++){
            cout<<x<<" ";
        }
        cout<<endl;
    }
    return 0;
}

Output

Enter the rows for Cube: 4
Enter the symbol or character: $

$ $ $ $
$ $ $ $
$ $ $ $
$ $ $ $

Explanation

When i=0 j will be running n times for each time j runs it will print * and after j has completed n number of times it will print a new line after that i=1 and again j will run n times this process will continue till i runs n number of times.

You can visit my cpp-language repo in github to see all the c++ program which I have written.

And do follow me on Github @jyotirmoydotdev