Programming a clock exercise

[Mike Reed]

Here's a little exercise for ya - participation voluntary.

You are a starship pilot and routinely make port at many different 

worlds. Each world's rotation is different; some slower, resulting 

in a longer day, and some faster resulting in a shorter one. 

Compounding the problem is the fact that the "Local governments" of 

these worlds have not adopted a "standard" 24 hour day. Some have 

20 "hours" some 25, etc, AND the "hour" does not necessarily have 

60 "minutes", nor a "minute" 60 seconds. You want to build an 

electronic watch (or clock) that you can set for the period (length 

of a day expressed in "Earth" hours), number of hours per period, 

number of minutes per hour, and number of seconds per minute. The 

clock will then accurately keep time for you on the planet you are 

visiting. The timekeeping abilities of this clock (and the 

programming language for it) are exactly the equivalent of an 

HP48-SX (see - i DID get HP calculator in there somewhere ;-)  

)Your task is to write the smallest program possible to make the 

clock work.

          Period

Planet    (std hrs)   Hrs/period  Min/Hr   Sec/min

Adaen     28.376      25          90       90

Baell     20.421      18          75       50

Calea     22.381      20          60       60

Dawaer    26.258      20          100      50

OK - you can throw rocks at me now...  ;oD

[Allen]

May I assume since the speed of the starship and the mass of the planets is not noted that relativestic time dilation effects are not to be corrected for in any of the the clocks? And that the standard SI unit for a second is consistent across the worlds. Alternatively, I could assume that "STD HRS" in the table above refers to a standard 3600 seconds that we might have on earth.

Edited: 8 Jan 2009, 8:47 p.m.

[Mike Reed]

Quote:

---

May I assume since the speed of the starship and the mass of the planets is not noted that relativestic time dilation effects are not to be corrected for in any of the the clocks?

Yes, discount relativistic dilation; the clock is for use while grounded on a planet - your starship's control console has a clock that is for use while in transit. :o)

And that the standard SI unit for a second is consistent across the worlds.

NO - that's the problem. The duration of each unit hour/minute/second is different on each world and none correspond to the same units on earth. For instance on the planet Adaen, whose rotational period is 28.376 EARTH hours, their day is divided into 25 local hours, each consisting of 90 local minutes which in turn consist of 90 local seconds. The rotational period of Adaen is 25.000 Adaen hours.

Alternatively, I could assume that "STD HRS" in the table above refers to a standard 3600 seconds that we might have on earth.

Yep; STD HRS refer to time as measured HERE on good old Terra Firma!

---

[David Hayden]

What is desired accuracy of the clock? For example, one Adaen second is about 4132.55 ticks of the HP 49's clock (which has 8192 ticks per earth second). So if I round off to 4133 ticks per Adaen second then I can get an answer, but it will drift, being off my 11.59 earth seconds after one Adaen day. Not much of a clock.

At the other extreme, we could say that the clock should run for eternity and remain accurate to within one clock tick forever. That's a bigger challenge.

[Mike Reed]

Quote:

---

What is desired accuracy of the clock? For example, one Adaen second is about 4132.55 ticks of the HP 49's clock (which has 8192 ticks per earth second). So if I round off to 4133 ticks per Adaen second then I can get an answer, but it will drift, being off my 11.59 earth seconds after one Adaen day. Not much of a clock.

True - not much of a clock... I'm only looking for "wristwatch" accuracy here, not "atomic clock". My Casio G-Shock is good for about 7 seconds a week which should be fine. Looking at the numbers for Adaen, it appears it may be necessary to add or subtract (4133/11.59)/25 "leap" ticks each hour to keep a reasonable accuracy in the timepiece. The clock program should calculate this itself, and take care of it for you.

At the other extreme, we could say that the clock should run for eternity and remain accurate to within one clock tick forever. That's a bigger challenge.

That would be a MUCH bigger challenge, especially within the parameters of the problem, as i don't THINK the HP48sx has a Caesium clock in it! LOL

---