ranger@ecsvax.UUCP (Rick N. Fincher) (05/07/87)
Apple II ProD TN #1: GETLN Input Buffer and ThunderClock Written by: 7/83 Modified by: Pete McDonald 11/85 The ThunderClock is automatically supported by ProDOS when ever it is identified as installed in the system. When programming under ProDOS, always consider the ThunderClock's impact on the GETLN input buffer ($200 - $2FF). ProDOS can support other clocks which may also use this space. When ever the ThunderClock receives a call from ProDOS, it deposits an ASCII string in the GETLN input buffer of the form: 07,04,14,22,46,57 which translates as: 07 = The month, JULY (01=JAN,...,12=DEC) 04 = The day-of-the-week, THURS.(00=SUN,...,06=SAT) 14 = The date, 14th (00 to 31) 22 = The hour, 10PM (00 to 23) 46 = The minute (00 to 59) 57 = The second (00 to 59) ProDOS calls the ThunderClock as part of many of its routines. Anything in the first 17 bytes of the GETLN input buffer is subject to loss if a ThunderClock is installed and gets called. It has been the practice of programmers, in general, to use the GETLN input buffer for every conceivable purpose. Therefore, an application should never store anything there. If your application has future need to know about the contents of the $200-$2FF space, it should be transferred to some other location to guarantee it will remain intact, particularly under ProDOS where a ThunderClock may regularly be overwriting the first 17 bytes.