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The sieve of eratosthenes

polyglot page

      IDENTIFICATION DIVISION.
      PROGRAM-ID.    SIEVE-PROG.
      * Sieve of Eratosthenes in Cobol
      * Written by Rob Hoelz

        ENVIRONMENT DIVISION.
        CONFIGURATION SECTION.
        INPUT-OUTPUT SECTION.

        DATA DIVISION.
        WORKING-STORAGE SECTION.
        01  Lim                PIC 9(6).
      * Change this number and recompile if you want to generate
      * primes over 1 million.  You'll also need to change the
      * picture clauses for Lim, Offset, CurrPrime, CurrPrime-Squared,
      * and Output-Value.
        01  PrimesTable.
            02  Primes             PIC 9(1) OCCURS 0 TO 1000000 TIMES
            DEPENDING ON Lim.
        01  Offset             PIC 9(6).
        01  CurrPrime          PIC 9(6).
        01  CurrPrime-Squared  PIC 9(6).
        01  Output-Value       PIC Z(5)9.
        PROCEDURE DIVISION.
           ACCEPT Lim FROM ARGUMENT-VALUE
               ON EXCEPTION
                   STOP RUN
           END-ACCEPT.

           SET Primes(1) TO 0.
           SET Offset TO 2.
           PERFORM WITH TEST BEFORE
               UNTIL Offset IS GREATER THAN Lim
               SET Primes(Offset) TO 1
               ADD 1 TO Offset
           END-PERFORM

           SET CurrPrime TO 2.
           MULTIPLY CurrPrime BY CurrPrime GIVING CurrPrime-Squared.
           PERFORM WITH TEST BEFORE
               UNTIL CurrPrime-Squared IS GREATER THAN Lim
               MULTIPLY CurrPrime BY 2 GIVING Offset
               PERFORM WITH TEST BEFORE UNTIL Offset > Lim
                   SET Primes(Offset) TO 0
                   ADD CurrPrime TO Offset
               END-PERFORM

               ADD 1 TO CurrPrime GIVING Offset
               PERFORM WITH TEST BEFORE
                   UNTIL Primes(Offset) IS EQUAL TO 1

                   ADD 1 TO Offset
               END-PERFORM
               SET CurrPrime TO Offset

               MULTIPLY CurrPrime BY CurrPrime GIVING CurrPrime-Squared
           END-PERFORM

           SET Offset TO 1.
           PERFORM WITH TEST BEFORE
               UNTIL Offset IS GREATER THAN Lim

               IF Primes(Offset) IS EQUAL TO 1 THEN
                   SET Output-Value TO Offset
                   DISPLAY Output-Value " " WITH NO ADVANCING
               END-IF

               ADD 1 TO Offset
           END-PERFORM
           DISPLAY "".
        STOP RUN.

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