Try this.
Code:
#include <iostream.h>
#include <iomanip.h>
int main ()
{
int score,
totalscore,
counter,
execute;
double avgscore;
execute = 999;
counter = 0;
totalscore = 0;
cout << "Intruction: \nEnter score range from 0 - 100 \nAfter that enter 999 for average score calculation " << endl;
cout << "Now enter a score: " ;
cin >> score;
do {
while ( score < 0 || score > 100 )
{
cout << "Error, input again " << endl;
cout << "Enter a score: " ;
cin >> score;
};
totalscore += score;
counter++;
cout << "Enter next score: ";
cin >> score;
} while ( score != execute );
avgscore = totalscore/counter;
cout << "The average score is: " << avgscore << endl;
return 0;
}