xerox 19771026 Time-of-Day Facilities For D0 free download

File name 19771026_Time-of-Day_Facilities_For_D0.pdf

To D. Liddle Date October 26, 1977 From H. C. Lauer Location Palo Alto Subject Time-of-Day facilities for DO Organization SOD/SO Y" XEnOX SDD ARCHIVES XEROX I have read and understood Pages _________ To _________ Reviewer Date_ _ __ Filed on: Clock.memo # of Pages Ref. 116/)J)~3 7/ In discussions with Brian Rosen, I have been told that it is possible and relatively easy to include a reliable, battery-powered, Time-and-Date clock in the DO at low cost. This consists of a digital watch chip mounted on the processor board. Such clocks typically report the time (and date?) with a precision of one second and an accuracy of a few seconds per month. I propose that we take fomal steps to have such a clock included in the DO for the following reasons: L The need to know the time of day is pervasive throughout the operating system and applications. In dozens of cases, documents, files, printed copies, and the display will be stamped with the time and date of important events in their lives. Either we have a time of day clock readily avaliable, or we simulate one using other, less satisfactory timing facilities. 2. If the time and date are not available internally (or from a server on the Xerox Wire), then the customer will be burdened with the nuisance of having to enter it each time he turns on the power to his system element. This is a small but perceptible inconvenience which our competitors could exploit. 3. A human-supplied time and date can be (and usually is) wildly inaccurate. This may affect the design of applications, and it certainly imposes a requirement that they be very robust against such inaccuracy. In particular, values reported by the timing software on a system element would not be guaranteed to be "ordered in time" across a power-down. (For example, it would not be safe to assume that one version of a document predates another because it has an earlier time stamp from the same system element -- particularly if the difference were, say, 364 days.)