1. Dedication of Duty

2. Important!
Every function should have a singular task to perform and no more.

3. Examples if (x >= 0) root = square_root(x);
do {     cout<<"enter nonnegative number: "<<endl;     cin>>num; } while (num < 0); root = square_root(num);
if ( f(x) < 0 )     exit (1); root = square_root(f(x));

4. Examples if (x >= 0) root = square_root(x);
do {     cout<<"enter nonnegative number: "<<endl;     cin>>num; } while (num < 0); root = square_root(num);
if ( f(x) < 0 )     exit (1); root = square_root(f(x));

5. Examples if (x >= 0) root = square_root(x);
do {     cout<<"enter nonnegative number: "<<endl;     cin>>num; } while (num < 0); root = square_root(num);
if ( f(x) < 0 )     exit (1); root = square_root(f(x));

6. End of Session