Basic Math Challege OOP344

A student was asking about "sscanf" and how it works for the week 3 ToDo (basicMath challenge), so here is the example:
#include <cstdio>
#include <iostream>
using namespace std;

int main(){
  double d;
  char num1[80] = "1234.5678";
  char num2[80] = "1234.5678a";
  char num3[80] = "12a34.5678";
  char num4[80] = "a1234.5678";
  char ch ;
  int ret;
  d = 0.0;
  ch = 'X';
  ret = sscanf(num1,"%lf%c", &d, &ch);
  cout<<ret<<endl;
  cout<<ch<<endl;
  cout<<d<<endl;
  cout<<"----------------------------"<<endl;
  d = 0.0;
  ch = 'X';
  ret = sscanf(num2,"%lf%c", &d, &ch);
  cout<<ret<<endl;
  cout<<ch<<endl;
  cout<<d<<endl;
  cout<<"----------------------------"<<endl;
  d = 0.0;
  ch = 'X';
  ret = sscanf(num3,"%lf%c", &d, &ch);
  cout<<ret<<endl;
  cout<<ch<<endl;
  cout<<d<<endl;
  cout<<"----------------------------"<<endl;
  d = 0.0;
  ch = 'X';
  ret = sscanf(num4,"%lf%c", &d, &ch);
  cout<<ret<<endl;
  cout<<ch<<endl;
  cout<<d<<endl;
  cout<<"----------------------------"<<endl;
  return 0;
}
output:
1
X
1234.57
----------------------------
2
a
1234.57
----------------------------
2
a
12
----------------------------
0
X
0

----------------------------