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 Creating demonstration versions
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 Blinker allows the developer to create a demonstration version of a DOS or
 DOS extended program at link time. It does this by providing commands which
 specify a maximum time in minutes for the program to run, or an expiration
 date for the software, or both. When either of these limits is exceeded, the
 processing of the program is halted and a demonstration termination message
 is displayed by the Blinker error handler.

 The default Blinker error handler is automatically linked into the program
 by Blinker. The error handler is called when an error occurs in the Blinker
 overlay manager, or when a demonstration limit set at link time has expired.
 Should you want to modify the termination message, or the result of
 termination processing, the source for the error handler has been provided.
 See the appropriate section earlier in this chapter for more information on
 the error handler.

 Note: For real mode programs, the demonstration restrictions are only
 checked by Blinker's overlay manager when overlays are executed, as Blinker
 has no control over procedures in the root. Therefore, if a real mode
 program is to be limited using these features, it must contain at least one
 overlaid procedure or function which is called regularly.

 Tips for using demo features

 . In the case of an incrementally-linked program under CA-Clipper,
   establishing or changing a demo feature requires a full re-link of the
   program, either by turning off incremental linking or deleting the program's
   .BIF or .EXE file.

 . For CA-Clipper programs, some non-CA-Clipper code must be overlaid
   for demo features to take effect, for instance EXTEND.LIB.

 . Very small .OBJ files placed in the overlay area may actually be
   removed to the root by Blinker if they are smaller than the default BLINKER
   OVERLAY THRESHOLD. Therefore, ensure the program contains at least one
   overlaid .OBJ which is larger than this default value.

 Demonstration date limit

 A program may be restricted so that it will no longer run after a specified
 date. The program then compares the specified expiration date with the
 system date, and when the former is greater than, or equal to, the latter,
 the error handler procedure BLERRPRG is called to terminate the program.
 To set the expiration date for a program, include the command

 BLINKER DEMONSTRATION DATE <yyyy/mm/dd>

 in the link script file, where mm represents the month, dd represents the
 day and yyyy represents the year; after this date the program will no longer
 run.

 Demonstration time limit

 A program may be restricted so that after the program has been running for a
 specified time in minutes, it will call the error handler procedure
 BLERRPRG, which terminates the program. The time counter is reset after each
 run, so the program can be re-run as many times as is desired for the same
 length of time.
 To restrict the execution time for a program include the command

 BLINKER DEMONSTRATION MINUTES <nuLimit>

 in the link script file. The number of minutes is specified in decimal and
 may be up to 65535 (any larger number will be ignored).