The clock command procedure works on a VT100 and looks alot nicer if the
terminal has the advance video option.

There are 2 paramaters to the procedure.  The first is the update time delay
and the second is the alarm time ( optional ).  On the command line neither
parameter is present then the user will prompted for both of parameters.
The good values for the first parameter are 01 to 59. This is the number of
seconds waited ( idle ) between updates. The second parameter is the alarm
time in 24 hour format. At alarm time the bell is rung and the command
procedure exits.  The clock will exit when user types control-Y, this is
very useful if there is no alarm time given. The user can type return to both 
the prompts and use the defaults which are 50 second update delay and no alarm
time.  The user can also enter the parmeters on the command line.  If only
the first parameter is present then a null second parameter is assumed
and no alarm time is set.  For exaple I have a DCL sysbol "c" defined to be
"@CLOCK.COM 10".   All parameters are checked for correctness and if an invalid
parameter is found the user is given an error message and prompted for the
value.