Confused about an exercise in my book

I need to be able to have the objects within the array be valid or invalid/ have value or have no value.

So if the user entered only 5 accounts out of 10 possible, it would throw away the last 5 that do not have any value what开发者_JS百科 so ever, so as to not ask for a computed interest for an account that doesn't exist.

How do I do this?

#include <iostream>
#include <iomanip>

using namespace std;

class BankAccount
{
private:
int accountNum;
double accountBal;
static const double annualIntRate;
public:
void enterAccountData(int, double);
void computeInterest();
void displayAccount();
};
//implementation section:
const double BankAccount::annualIntRate = 0.03;
void BankAccount::enterAccountData(int number, double balance)
{
cout << setprecision(2) << fixed;



cout << "Enter the account number " << endl;
cin >> number;
accountNum = number;
while(number < 0 || number < 1000)
{
    cout << "Account numbers cannot be negative or less than 1000 " <<
        "Enter a new account number: " << endl;
    cin >> number;
}

cout << "Enter the account balance " << endl;
cin >> balance;
accountBal = balance;
while(balance < 0)
{
    cout << "Account balances cannot be negative. " <<
        "Enter a new account balance: " << endl;
    cin >> balance;
}
return;
}
void BankAccount::computeInterest()
{
const int MAX_ACCOUNTS = 10;
const int MONTHS_IN_YEAR = 12;
int months;
double rate = 0; 
int counter = 0;

cout << endl << "How many months will the account be held for? " << endl;
cin >> months;
counter = 0;
do
{
 accountBal = accountBal * annualIntRate + accountBal;
 counter++;
}while(months > counter);

cout << endl << "Account # " << accountNum << " 's balance is:$" << accountBal << endl;
}

int main()
{
const int QUIT = 0;
const int MAX_ACCOUNTS = 10;
int counter;
int input;
int number = 0;
double balance = 0;

BankAccount accounts[MAX_ACCOUNTS];
//BankAccount display;

counter = 0;

do
{
    accounts[counter].enterAccountData(number, balance);
    cout << " Enter " << QUIT << " to stop, or press 1 to proceed.";
    cin >> input;
    counter++;

}while(input != QUIT && counter != 10);

for(counter = 0; counter < MAX_ACCOUNTS; counter++)
{
    accounts[counter].computeInterest();
}
system("pause");
return 0;
}

You should try tonarrow down your questions to just what you are really asking, this is a little confusing to look at.

After the first loop, have it "remember" what value for counter it managed to reach, and then in the second loop only iterate up to that, instead of up to MAX_ACCOUNTS.

And converting from months to years is just dividing by 12 no?

It seems you have skipped the chapters about Arrays. Re-read it!

ps. surely 0 < 1000 while(number < 0 || number < 1000)

void BankAccount::enterAccountData(int number, double balance). What is the need for the two arguments ? Take the input directly for the member variables. Unnecessary operations are commented. This would also do the job -

void BankAccount::enterAccountData()
{
    cout << setprecision(2) << fixed;

    cout << "Enter the account number " << endl;
    cin >> accountNum; // Take input directly to accountNum
    //  accountNum = number;  // No need of this assignment
   while(accountNum < 0 || accountNum < 1000)
   {
       cout << "Account numbers cannot be negative or less than 1000 " <<
    "Enter a new account number: " << endl;
       cin >> accountNum;
   }

   cout << "Enter the account balance " << endl;
   cin >> accountBal;
   //  accountBal = balance; // Unnecessary assignment
   while(accountBal < 0)
   {
       cout << "Account balances cannot be negative. " <<
    "Enter a new account balance: " << endl;
       cin >> accountBal;
   }
   //  return;  // What is the need of this return statement? Method signature says
                // it doesn't return anything.
}

When you think of declaring variables, think of whether they are necessary. Unnecessary declaring and assigning the variables make the problem looks complex and is the source of confusion. Think simple :)