CLOCK$ I/O Structure

 Programs can open the CLOCK$ device (via DOS fn 3dH) and use fn 3fH (read
 file) to read the system time or fn 40H (write to file) to change it.

 The format of all reads and writes to this device is a 6-byte (48-bit)
 binary value indicating the number of milliseconds since January 1, 1980.
 1000 milliseconds = 1 second; highest value is (2^48)-1 or 8915.7 years.

  Offset Size Contents
  ▀▀▀▀▀▀ ▀▀▀▀ ▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀
   +0      2  wLowMs       least significant word (bits 0-15)
   +2      2  wMidMs       middle word (bits 16-31)
   +4      2  wHighMs      most significant word (bits 32-47)
           6               Size of ClockIORec

 Writing to CLOCK$ changes all parts of the structure.  It is much more
 sensible to use DOS fns 2bH (set date) and 2dH (set time), which perform
 the same task, but without the headaches.

See Also: Device Drivers
          Device Attribute
          Device Requests