Classes

• public - may be accessed inside the class and by any other class
• protected - may be accessed inside the class and by any class derived from this class
• private - may be accessed inside the class and by friend

      class Matrix {
        private:
          double *_array;       // internal matrix representation
          int _nr;              // number of rows
          int _nc;              // number of columns

          void no_op ( void );  // private function

        public:
          int foo;              // public variable

          // constructor
          Matrix (int nrows, int ncols);

          // destructor
          virtual ~Matrix ();

          // get a specific value from the matrix
          double getVal ( int row, int col ) const;

          // set a specific value in the matrix
          void setVal ( int row, int col, double val );

          // add another matrix to this matrix
          Matrix& operator+ (const Matrix& b);

          // print out the matrix on the specified stream
          friend ostream& operator<< ( ostream& os, const Matrix& m );
      };