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    Length: 2432 (0x980)
    Types: TextFile
    Names: »PRIMES.PRN«

└─⟦314366c8f⟧ Bits:30009789/_.ft.Ibm2.50006598.imd Mogens Pelles Zilog 80,000 / EOS projekt
    └─⟦this⟧ »PRIMES.PRN« 

TextFile

Pro Pascal Compiler - Version zz 2.1

Compilation of: primes.PAS

Options:    LNIAPG

    1   0000    PROGRAM primes(input,output);
    2   0000    æComputes primes up to a given limit,  
    3   0000     using the "sieve of Eratosthenes" å
    4   0000    CONST
    5   0000      maxnumber = 32767;
    6   0000      maxhalf = 16383;  æmaxnumber DIV 2å
    7   0000    TYPE
    8   0000      number = 1..maxnumber;
    9   0000      half = 1..maxhalf;
   10   0000    VAR
   11   0000      count,factor,maxfactor,limit,nonprime: number;
   12   0000      index,halflimit: half;
   13   0000      primeflags: ARRAY ÆhalfÅ OF boolean;
   14   0000    BEGIN
   15   0000      REPEAT
   16   000E        writeln('Upper limit = ?');
   17   0035        readln(limit);
   18   004C      UNTIL (1 <= limit) AND (limit <= maxnumber);
   19   0072      halflimit := pred(limit) DIV 2;
   20   0097      FOR index := 1 TO halflimit DO primeflagsÆindexÅ := true;
   21   00CB      æIf a number is composite, at least one of its factors is 
   22   00CB       less than or equal to its square root, so: å
   23   00CB      maxfactor := round(sqrt(limit));
   24   00EF      count := 2;  æcount of primes: 1 and 2 are the first twoå
   25   00FA      factor := 1;  æfirst actual factor used will be 3å
   26   0105      FOR index := 1 TO halflimit DO
   27   0123        BEGIN
   28   0128          factor := factor + 2;  æi.e. factor := 2*index + 1å
   29   014A          IF primeflagsÆindexÅ THEN
   30   015E            æA new prime has been found å
   31   015E            BEGIN  count := succ(count);
   32   0178              æIf necessary, cross out all its multipleså
   33   0178              IF factor <= maxfactor THEN
   34   018D                BEGIN  nonprime := index + factor;
   35   01B2                  WHILE nonprime <= halflimit DO
   36   01C7                    BEGIN
   37   01CC                      primeflagsÆnonprimeÅ := false;
   38   01DD                      nonprime := nonprime + factor;
   39   0202                    END æWHILEå;
   40   0205                END;
   41   0205              writeln(factor);      æomitted for timingå
   42   0221            END æIFå;
   43   0221        END æFORå;
   44   022F      writeln('Number of primes up to ',limit,' = ',count);
   45   0290    END.
«eof»