Three main function to control Trading Automatic

Good day to all of Us,
Still fresh in mymemory at the first time when I start to recognize Automatic Trading Programming.
My Mentor say :" Don't worry ,it will be EASY,we just need THREE MAIN fUNCTION, as below
//+------------------------------------------------------------------+
//| expert initialization function |
//+------------------------------------------------------------------+
int init()
{
//----
//-- "FIRST FUNCTION"
//----
return(0);
}
//+------------------------------------------------------------------+
//| expert deinitialization function |
//+------------------------------------------------------------------+
int deinit()
{
//----
//-- " SECOND FUNCTION"
//----
return(0);
}
//+------------------------------------------------------------------+
//| expert start function |
//+------------------------------------------------------------------+
int start()
{
//----
//-- "THIRD FUNCTION"
//----
return(0);
}
//+------------------------------------------------------------------+

That's ALL.
So I begin to learn, learn and.................. learn It.

But at contrary condition, up to now day, still also I heard,
some 'Mocky Voice' say:" Automatic Trading Programming is EASY"
, but ???

So ,what do You think , how we can answer them,Two different ways of approach that considers all the things that's easy.