* //////////////////////////////////////////////////////////
* // Name: Peter M. Maurer
* // Program: Sieve of Eratosthenes
* // Due: Never
* // Language: COBOL
* //////////////////////////////////////////////////////////

       identification division.
       program-id. SieveE as "SieveE.SieveE".

       environment division.
       configuration section.
       repository.
       

       data division.
       working-storage section.
           77 i pic 99999.
           77 j pic 99999.
           77 Product pic 99999.
           77 Showit pic ZZZZZ.
           77 Candidates pic 99999 occurs 999.
       procedure division.
       Main_Part.
           Move 1 to I.
           Perform Init_1 999 times.
	       Move 0 to Candidates(1).
* start the sieve with the integer 1
	       Move 1 to i.
	       Perform Check_Number Until i >= 1000.
           Move 1 to i.
           Perform Print 999 times.
           goback.
       Init_1.
           Move 1 to Candidates(i).
           Add 1 to I.
       Check_Number.
* advance to the next un-crossed out number.
* this number must be a prime.
           Perform Advance Until i >= 1000 or Candidates(i) NOT = 0.
* Avoid running off the end of the data structure.
           if i >= 1000 EXIT.
           Move 2 to j.
           Multiply i by j giving Product.
* cross out all multiples of the prime, starting with 2*p.
           Perform Cross_Out Until Product >= 1000.
* go on to next prime.
           Add 1 to i.
       Advance.
           Add 1 to i.
       Cross_Out.
           Move 0 to Candidates(Product).
           Add 1 to j.
           Multiply i by j giving Product.
       Print.
           if Candidates(i) NOT = 0
               Move i to Showit
               Display Showit, " is prime.".
           Add 1 to i.
       end program SieveE.