const int LOW_END = 10;    // low end of incomes considered
const int HIGH_END = 100;  // high end of incomes considered
const int TABLE_SIZE = HIGH_END - LOW_END + 1;

typedef int tableType[TABLE_SIZE];

int Index(int Group)
// Returns the array index that corresponds to Group number.
{
   return Group - LOW_END;
}  // end Index

void ReadData(tableType IncomeData, int Low, int High,
              bool& DataError)

// ---------------------------------------------------------
// Reads and organizes income statistics.
// Precondition: The calling program gives directions and
// prompts the user. Each input line contains exactly two 
// integers in the form G N, where N is the number of 
// people with an income in the G-thousand-dollar group and
// Low <= G <= High. An input line with values of zero 
// for both G and N terminates the input.
// Postcondition: IncomeData[G-Low] = total number of people
// with an income in the G-thousand-dollar group. The values 
// read are displayed. If either G or N is erroneous (G and 
// N are not both 0, and either G < Low, G > High, or 
// N < 0), the function ignores the data line, sets 
// DataError to tRUE, and continues. In this case, the 
// calling program should take action. DataError is fALSE 
// if the data is error free.
// ---------------------------------------------------------
{
   int Group, Number;  // input values

   DataError = false;  // no data error found as yet

   for (Group = Low; Group <= High; ++Group)  // clear array
      IncomeData[Index(Group)] = 0;

   for (cin >> Group >> Number; 
        (Group != 0) || (Number != 0);
        cin >> Group >> Number)
   {  // Invariant: Group and Number are not both 0
      cout << "Input line specifies that income group "
           << Group << "\ncontains " << Number 
           << " people.\n";

      if ((Group >= Low) && (Group <= High) && (Number >= 0))
         // input data is valid -- add it to tally
         IncomeData[Index(Group)] += Number;

      else
         // error in input data: set error flag and
         // ignore input line
         DataError = true;
   }  // end for
}  // end ReadData