Scripts are programs that are intended to perform a single action. Unlike an indicator or Expert that works continually, a Script stops functioning once it has completed its function one time. Like Custom Indicators, Scripts are created, setup and launched in much the same manner as Experts. When launching the Experts Wizard, select "Scripts" as the object to be created. Continue in the same manner as creating an Expert or Custom Indicator (see the Expert Advisor Creation and Custom Indicator Creation sections of this tutorial).
To set up Script parameters, open the Options window and select the "Expert Advisors" tab. To open the window:
- In the Main Menu > Tools > Options; or
- Pressing CTRL + O on the computer keyboard.
- Allow live trading - to enable Experts in real-time mode (rather than testing an Expert on historical data).
- Ask manual confirmation - to send trade confirmation prior to submitting the order.
- Allow DLL imports -to use DLLs to enhance Expert functionality.
- Confirm DLL function calls - to allow control over the execution of each called function.
- Allow external experts imports - to allow the Expert to access functions from other Experts or MQL4 libraries.
A Script automatically shuts down once it has completed its function one time. Traders can, however, remove a Script manually. To remove a Script from a chart, right-click on the chart and select "Remove Script," as shown in Figure 20.
|Figure 20 - To remove a Script from a price chart, right-click on the chart and select "Remove Script" from the chart context menu.|
Options for Non-Programmers
People who are not interested in learning how to program in the MQL4 language can still take advantage of Experts, Custom Indicators and Scripts. A growing number of commercially available products can be purchased at various trading-related businesses online, and MT4 users can also hire a qualified MQL4 programmer to perform the coding.
It is important to note that when working with a programmer, all ideas must be quantifiable and objective. For example, if the trader wants to enter a long position when price goes above a moving average, he or she will have to specify the moving average length, the precise entry point (next bar on open, for example) charting interval and even the trading instrument. Most programmers will not accept jobs that entail a lot of guesswork on the part of the programmer, and so project specifications need to be absolutely clear.
In general, if a commercial Expert, Custom Indicator or Script has been purchased, it will come with specific installation instructions. Similarly, a programmer will typically include instructions for installation. It is always valuable to read the instructions before attempting the installation to avoid any complications.
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