Example of throwing exception

// account.h
// A banking account:
class Account { /*...*/ };

// An exception class:
struct AcctError {};

// main.cpp
#include <iostream>
void main() {
    Account acct( 1000.00 );
    try {
        acct.withdraw( 2000.00 );
    }
    catch ( AcctError& ex ) {
        std::cout << "Not enough funds";
    }
}

// account.cpp
void Account::withdraw( double amount )
{
    if ( amount > m_available_balance ) {
        // Not enough balance,
        // Unnamed temporary object:
        throw AcctError();
    }
    // Balance is ok, proceed...
}