矩阵中填数

#include <iostream>

using namespace std;

class CMatrix
{
public:
CMatrix(unsigned long m,unsigned long n);
CMatrix(CMatrix& A); // COPY构造函数，必须要。
CMatrix(){_m=0;_n=0;_data=NULL;}//无参数构造函数，必须要。
~CMatrix(){if(_data!=NULL)delete _data;}

void DisplayOnCMD();
bool SetCell(unsigned long x,unsigned long y,double data);
double GetCell(unsigned long x,unsigned long y);
unsigned long GetM(){return _m;}
unsigned long GetN(){return _n;}
CMatrix operator+(const CMatrix &A);
CMatrix operator=(const CMatrix &A);
private:
unsigned long _m,_n;
double* _data;
};

CMatrix::CMatrix(unsigned long m,unsigned long n)
{
_m=m;_n=n;
_data=new double[_m*_n];
for(int i=0;i<_m*_n;i++)
_data[i]=0;
}

CMatrix::CMatrix(CMatrix& A)
{
_m=A._m;_n=A._n;
_data=new double[_m*_n];
for(int i=0;i<