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CPM OPERATING SYSTEMS/CPM 3.X/CPM 3.0/Y2K PATCHES/CPM2000.DOC

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+CP/M 3: Year 2000 fixes
+=======================
+
+  The following archive contains all CP/M 3 .COM files that use dates,
+updated to operate correctly past the year 2000. They also allow dates to
+be in US or UK format.
+
+Operation: SETDEF
+=================
+
+  To use UK-format dates, type:
+
+SETDEF [UK]
+
+  To return to US-format dates, type:
+
+SETDEF [US]
+
+Operation: DATE
+===============
+
+  The year entered when dates are set can be 0-77 (meaning 2000-2077) or 78-99 
+(meaning 1978-1999). The problem of what to do in 2078 is deferred to a later
+revision of this program.
+
+  Dates are now displayed with four-figure years.
+
+  The US/UK setting applies to date entry and display.
+
+Operation: DIR and SHOW
+=======================
+
+  DIR and SHOW display years above 2000 correctly (rather than as ":0") and
+obey the US/UK setting.
+
+Technical
+=========
+
+  The US/UK setting is stored in a previously unused SCB byte. I have checked 
+all available sources on the SCB (including the BDOS source) to come up with
+the following:
+
+SCB + 0Ch  (xxA8h) bit 0: 0 for US, 1 for UK.
+
+  This address is shown in the BDOS source as the low byte of an unused word
+in the "Utilities" section of the SCB. ZPM3 does not use this byte either.
+
+  My recommendation is that any other expansions to utilities should use the
+remainder of this word to store settings.
+