简单的C++问题...电脑重装软件没了...帮忙编一下..谢谢!!

阅读下列程序段，写出正确执行结果.
4．
# include <iostream>
# include <iomanip>
using namespace std;
int main()
{
const float a=123.456789f;
const double b=123.456789;
cout<<a<<","<<b<<endl;
cout<<setprecision(3)<<a<<","<<b<<endl;
cout<<setprecision(6)<<a<<","<<b<<endl;
return 0;
}

7．
# include <iostream>
using namespace std;
int box_volume(int length,int width=2,int height=3);
int main()
{
int x=10,y=10,z=10;
cout<<box_volume(x,y,z)<<endl;
cout<<box_volume(x,y)<<endl;
cout<<box_volume(x)<<endl;
cout<<box_volume(x,7)<<endl;
cout<<box_volume(5,5,5)<<endl;
return 0;
}
int box_volume(int length,int width,int height)
{
cout<<lengt

第一题:
123.457,123.457
123,123
123.457,123.457
第二题:
10,10,10:1000
10,10,3:300
10,2,3:60
10,7,3:210
5,5,5:125
第三题:
General Function
Template Function
第四题:
2
2
第五题:

#include <iostream>

using namespace std;

const int M = 3;

void reverse_matrix (int a[M][M], int num)
{
int t = 0;
for (int i = 0; i < num; i++)
{
for (int j = i; j < num; j++)
{
t = a[i][j];
a[i][j] = a[j][i];
a[j][i] = t;
}
}
}

int main(int argc, char* argv[])
{
int a[M][M];
for (int i=0; i<M; ++i)
{
for (int j=0; j<M; ++j)
{
cin>>a[i][j];
}
}
reverse_matrix( a,M);
for (i=0; i<M; ++i)
{
for (int j=0; j<M; ++j)
{
cout<<a[i][j]<<' ';
}
cout<<endl;