BASIC Program

[jonesy29847]

I need to write a program that will send out the Modified Julian Date to a part marker. I will use the PLC date to calculate MJD.

I am thinking of using a lookup table, but want to field a few suggestions first.

Any ideas anyone.

 

[lrob]

If you use a lookup table what will you do with a leap year? Could you use some sort of incrementing counter that will reset on Jan 1 each year , then increment at 12:00 midnight. Then you use the year and the incremented date for you MJD.

 

[jonesy29847]

Sorry I should have been more specific. I will use 2 tables one for leap year and one for non-leap.

The only concern I have for counter is if the processor is placed in program mode during the time the date should change.

 

[lrob]

That is true and if the PLC is off for long periods of time. May be use the month as a quick reference then add whatever day of the month it is. For example if it is Mar 3 you would add 3 to 60(end of feb) for MJD of 63. Then you determine leap years and add a 1if the date is after Feb.

 

[jonesy29847]

Sounds interesting.

Thanks

 

[lrob]

You would have 11 move statements, depending on the month value from the PLC date. Move the correct value for the previous month into a register. Add the day value of the date of the current month to the register and that should give you your MJD. For a leap year you can program several compares to determine if the current year is a leap year. If it is you would just add 1 for any month date from 3 to 11.

 

[lrob]

Additional comment this is probably similar to what you would need to do to provide the index value for your lookup table.

 

[jonesy29847]

OK the program is done and has been tested. I built two lookup tables, one for leap years and one for non-leap years. The data took the form of Month, StartDay. I also had to determine if the current year was a leap year, the BASIC module did not support MOD division so I divided the year by 4 and if there was a remainder I used the non-leap look up table.

The module used was the 1746-BAS T module, using PBASE to program. PBASE has a nice translation feature that allows the program to be writen without line numbers. This was usefull in that the source code is easier to understand.

There is supposed to be a C translator available but I couldn't find it, C is much better to write code with.

Thanks to all for feedback.

 

[nbucska]

Calculation of the Gregorian date (which is easily
convertible to Julian) :

Nd ( # of day for Sun. to Sat.) = 0 to 6
Nm ( # of month, Jan to Dec, 1 digit ea. )
= 400 351 362 402 spaced for readability.
Ny ( # of year, 0 to 6 ) e.g. for 1949 and 2005 = 1
''' After each year and in a leapyear after Feb. 29, too
Ny=Ny+1: if Ny>6 then Ny=Ny-7
Nd = (Ny +Nm + D) mod 7

e.g. Nd(12/25/2005) = (1+2+25) mod 7 =28 mod 7=0 => Sunday



<nbucska@pcperipherals DOT com> subj: eng-tips