Question 1

#include <iostream>
using namespace std;

int main(){

        int n, i;

        cout << "n = ";
        cin >> n;

        for(i=n;i>=0;i--){
                cout << i << " ";
        }

        return 0;
}

Question 2

#include <iostream>
using namespace std;

int main(){

        int i;
        for(i=11;i<=22;i++){
                cout << "1/"<< i <<"=" << (float)1.0/i << endl;
        }

        return 0;
}

Question 3

#include <iostream>
using namespace std;

int main(){

        int i, sum=0, n;
        for(i=0;i<6;i++){
                cout << "Input number "<< i <<": ";
                cin >> n;
                sum = sum+n*n;
        }

        cout << "Sum of square = " << sum << endl;

        return 0;
}

Question 4

#include <iostream>
using namespace std;

int main(){

        int n, m, i;

        cout << "Enter m: ";
        cin >> m;
        do{
                cout << "Enter n: ";
                cin >> n;
        }while(n<=m);

        if(m%2==0)
                m = m+1;
        for(i=0;i<=n-m;i+=2){
                if(i%5==0)
                        cout << endl;
                cout << i+m << "\t";
        }
        cout << endl;

        return 0;
}

Question 5

#include <iostream>
using namespace std;

int main(){

        int i, j;

        for(i=1; i<10; i++){
                for(j=1;j<10;j++)
                        cout << i*j << "\t";
                cout << endl;
        }

        return 0;
}

Question 6(a)
#include <iostream>
using namespace std;

int main(){

        int n, i, j;

        do{
                cout << "n = ";
                cin >> n;
        }while(n<=0||n>20);

        for(i=1;i<=n;i++){
                for(j=1;j<=i;j++)
                        cout << i << " ";
                cout << endl;
        }
        return 0;
}

Question 6(b)
#include <iostream>
using namespace std;

int main(){

        int n, i, j;

        do{
                cout << "n = ";
                cin >> n;
        }while(n<=0||n>20);

        for(i=1;i<=n;i++){
                for(j=1;j<=i;j++)
                        cout << j << " ";
                cout << endl;
        }

        return 0;
}

Question 6(c)
#include <iostream>
using namespace std;

int main(){

        int n, i, j;

        do{
                cout << "n = ";
                cin >> n;
        }while(n<=0||n>20);

        for(i=1;i<=n;i++){
                for(j=1;j<=i;j++)
                        cout << (char)('a'+j-1) << " ";
                cout << endl;
        }


        return 0;
}