/*
  protected should be used to prevent a clumsy programmer from harming
  things.

  If the programmer is allowed to access the array "data", he could write
  A.data[36127] = 44, and who knows what would be ruined.

  Also, if the programmer is allowed to access size, she could write
  A.size = 36128; A.data[36127] = 44, and cause the same trouble. Sometimes
  it is not obvious that a simple variable should be protected,and thought
  is required.
*/


#include <iostream>

struct safearray
{ protected:
    int data[100];
    int size;

  public:

  int getsize()
  { return size; }

  void setsize(int s)
  { if (s<0 || s>100)
    { cerr << "error in get\n";
      exit(1); }
    size = s; }
 
  int get(int pos)
  { if (pos<0 || pos>=size)
    { cerr << "error in get\n";
      exit(1); }
    return data[pos]; }
 
  void put(int pos, int val)
  { if (pos<0 || pos>=size)
    { cerr << "error in put\n";
      exit(1); }
    data[pos] = val; }
};

void main()
{ safearray A, B;
  A.setsize(20);
  B.setsize(90);
  cout << "A\n";
  for (int i=0; i < A.getsize(); i+=1)
    A.put(i, i * 10001);
  cout << "B\n";
  for (int i=0; i < 123; i+=1)
    B.put(i,  i*2); }