It was explain in this post http://www.forex-tsd.com/148466-post759.html

I am a newbie and don't know anything about programming. So here it goes -what is a .mq4 file, what does it do and where do I put it. Also, what's the difference between an mq4 file and a .ex4. By playing around with it I have noticed that some .mq4 will also place trades. Any info is much appreciated.
You guys are so knowledgeable and helpful, giving so generously of your time.
Thanks in advance.
forexhog

I moved your post to this thread.
For all the answers please read this thread How to start with MetaTrader and forex

The mq4 file is the one can be modified by coders.

The ex4 file is the compiled one used in your platform.

Both are in the same folder (experts or indicators or script)

FerruFx

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Im looking at the documentation on how to code in MT4.

Are all the conditions being checked tick by tick or compare to previous bar etc? So far it seems like the condition is being checked tick by tick.
If yes, this is what I want.

Also what do I code if I also want to check the condition of previous 5 bars's close?

Thanks.

Look at this thread How to start with MetaTrader and forex

To say shortly, the coders are coding the systems on close bar. Almost always. There are some few exceptions related to open bar scalpers and so on.

What is coding on close bar?
It is the same with real manual trading: the signal is valid if you see it on previous(or close) bar.
Numeration is started with bar number 0 (current open bar). In this case previous bar is bar #1 and so on.

It is no any programming problem to check the condition of previous 5 bars's close.

Check this thread (first post) for more information How to start with MetaTrader and forex

hi nd,
thx for all the so much valuable info in this thread,
i`m glad that mt4 is the best platform for forex trading compare to others,
my question is can we change the currency pair with the same mt4 setup directly without looking back for template?

Just the templates and profiles default only.

Thanks for the info.

I have an issue. In terms of closing price, for previous bars, it is very obvious. What about the closing price of a current bar, the normal calculation is the last price will be the closing price to be calculated, am I right on this? Lets say I am using 30 min chart, time is 14:12:35, the normal coding is calculating the tick at 14:12:35, then the previous close would be any tick just before this time or the completed_closed_price at 14:00:00? This is where Im confused when Im coding.

In another secenio, I actually want to compare the close price at different closing level. Using the above same time, I want to compare the close price at 14:12:35 and the closing price at 14:00:00, 13:30:00, 13:00:00 etc.

I think there are 2 ways to code to accomplish these 2 different secenio.

Please point out the coding differences between these 2, just a few code no need the whole code so I can get the idea. I dont really get it by reading the documentation.

Thanks.

When we are talking about closing price so we are talking aqbout indicators' condition. It means that one indicator's line is crossing the other indicator's line ... and it should be on closed bar (or previous bar).
Or just arrow which you see on the bar ... so this arrow is programmed on closed bar (previous bar).

Of course there are many exceptions but those exceptions are some special cases.

As to exit so if take profit or stop loss so it is market price.

Sorry if it is not helping so much ...