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with Turbo Pascal
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Converting Attract Mode into Main Program

For monoprogram form, the attract must be converted into the main program of the entire dialogue, from which the modules are called as procedures. It must take care of at least:

• Initialising Turbo Pascal's overlay system.
• Choosing and declaring which of the units the entire program uses to overlay. Note that, since only the program can do this (units cannot make this choice, even about other units they themselves use), even units which the attract program does not directly use or see must be declared overlaid if they are to be managed as overlays.
• checking whether a module has already been chosen to run; in this case the module should be called at once, with no presentation of the attract mode or menu.
• creating a safe target to which Ports' routine ChainTo can jump when exiting module code. See the addendum for Turbo Pascal to the Ports Unit reference guide.
• re-initialising those units (such as utility units) which each module expects to be freshly initialised before it runs.

The format of the program is:

USES Overlay, AttrXtra, MarkJump, ..., Ports, PDisplay,...;
    BEGIN
      WhichModule := 0;
      REPEAT
        MarkFilesOpen( dgTargetMark[1] ); {Make a note of the DOS 
              file handles that are open just before a module starts. }
        ReturnCode := SetJmp( dgTargetMark[1]);  {
        IF LENGTH(NextModuleNamed) = 0 THEN 
      UNTIL WhichModule > LastModule;
    END;

• Making and Using the Overlays
• The Module-Calling Cycle
• Cleaning up after Modules
• State Machine