By checking the System.totalMemory property, you can determine the amount of memory (in bytes) that Flash Player or AIR is currently using. This property allows you to monitor memory usage and optimize your applications based on how the memory level changes. For example, if a particular visual effect causes a large increase in memory usage, you may want to consider modifying the effect or eliminating it altogether.

The System.ime property is a reference to the currently installed Input Method Editor (IME). This property allows you to listen for imeComposition events (flash.events.IMEEvent.IME_COMPOSITION) by using the addEventListener() method.

The third property in the System class is useCodePage. When useCodePage is set to true, Flash Player and AIR use the traditional code page of the operating system that is running the player to load external text files. If you set this property to false, you tell Flash Player or AIR to interpret the external file as Unicode.

If you set System.useCodePage to true, remember that the traditional code page of the operating system running the player must include the characters used in your external text file in order for the text to display. For example, if you load an external text file that contains Chinese characters, those characters cannot display on a system that uses the English Windows code page because that code page does not include Chinese characters.

To ensure that users on all platforms can view the external text files that are used in your SWF files, you should encode all external text files as Unicode and leave System.useCodePage set to false by default. This way, Flash Player and AIR interpret the text as Unicode.

The System class includes a method called setClipboard() that allows Flash Player and AIR to set the contents of the user’s clipboard with a specified string. For security reasons, there is no Security.getClipboard() method, since such a method could potentially allow malicious sites to access the data last copied to the user’s clipboard.

The following code illustrates how an error message can be copied to the user’s clipboard when a security error occurs. The error message can be useful if the user wants to report a potential bug with an application.

private function securityErrorHandler(event:SecurityErrorEvent):void 
{ 
    var errorString:String = "[" + event.type + "] " + event.text; 
    trace(errorString); 
    System.setClipboard(errorString); 
}