sieve.a60

b̲e̲g̲i̲n̲
    c̲o̲m̲m̲e̲n̲t̲ zeef van Erathostenes;
    i̲n̲t̲e̲g̲e̲r̲ p, m;
    b̲e̲g̲i̲n̲
        B̲o̲o̲l̲e̲a̲n̲ a̲r̲r̲a̲y̲ prime [2 : 1000000];

        PRINTTEXT(`Computing primes...');
        f̲o̲r̲ p := 2, 3 s̲t̲e̲p̲ 2 u̲n̲t̲i̲l̲ 1000000 d̲o̲
            prime[p] := t̲r̲u̲e̲;
        PRINTTEXT(`.');
        f̲o̲r̲ p := 2, 3 s̲t̲e̲p̲ 2 u̲n̲t̲i̲l̲ 1000 d̲o̲ b̲e̲g̲i̲n̲
            i̲f̲ prime[p] t̲h̲e̲n̲
                f̲o̲r̲ m := p * p s̲t̲e̲p̲ p u̲n̲t̲i̲l̲ 1000000 d̲o̲
                    prime[m] := f̲a̲l̲s̲e̲;
            i̲f̲ p ÷ 100 * 100 + 1 = p t̲h̲e̲n̲
                PRINTTEXT(`.');
        e̲n̲d̲;
        NLCR;

        m := 0;
        f̲o̲r̲ p := 2, 3 s̲t̲e̲p̲ 2 u̲n̲t̲i̲l̲ 1000000 d̲o̲ b̲e̲g̲i̲n̲
            i̲f̲ prime[p] t̲h̲e̲n̲ b̲e̲g̲i̲n̲
                m := m + 1
            e̲n̲d̲
        e̲n̲d̲;
        PRINTTEXT(`Number of primes below 1000 000: ');
        print(m);
        NLCR
    e̲n̲d̲
e̲n̲d̲