enums Will Save the Day
The most important contribution of this technique is in the event-dispatcher. Instead of using meaningless numbers as array indexes, you can now use mnemonic enumerators:

switch (icon_code)
{
case IC_Send:
dispatch(mail, options[send]);
break;
case IC_Reply:
dispatch(mail, options[reply]);
break;
case IC_Forward:
dispatch(mail, options[forward]);
break;
//..
case IC_Save:
dispatch(mail, options[save]);
break;
case IC_Help:
showOnlineHelp();
break;
}

As a bonus, detecting typos is much easier now:

case IC_Save:
dispatch(mail, options[save]);
break;
case IC_Print:
dispatch(mail, options[save]);//a typo!

But That's Not All!
enum types offer two benefits over const int values: they automatically assign consecutive values to enumerators and they are strongly typed. Thus, if you declare a function that returns an enum:

mail_ops getUserClick();

The compiler can easily catch silly mistakes like this one:

mail_ops getUserClick()
{
return 20; //error
}

Some compilers are even clever enough to warn about missing enumerators in a switch statement.