Prime Sieve in Action created with LOGO

TO PRIMES
FS CS HT PU
SETPC 12 SETFONT "TIMES 16 1
SETXY [-85 220] PD TT [PRIME SIEVE]
SETPC 1 SETFONT "COURIER 12 1
PRNTARRAY 2
SIEVE 2 2
SIEVE 3 3
SIEVE 5 5
SIEVE 7 7
SIEVE 11 11
SIEVE 13 13
WAITKEY CS SS
END

TO PRNTARRAY :N
IF :N 200 [STOP]
PU SETXY CALCPOS :N PD
TT :N
PRNTARRAY :N + 1
END

TO SIEVE :N :I
IF :I * :N 200 [STOP]
SETPC 12
PU SETXY CALCPOS :I * :N
PD TT :N * :I TONE :N * 80 4
SETPC 7 TT :N * :I
SIEVE :N :I + 1
END

TO CALCPOS :N
MAKE "X (4 * REMAINDER (:N - 1) 10)
IF :N <10 [MAKE "X :X + 1]>
IF :N <100 [MAKE "X :X + 1]>
MAKE "Y (INT (:N - 1) / 10)
OP LIST 10 * :X - 220 180 - 20 * :Y
END

TO WAITKEY
IF KEY? [STOP]
WAITKEY
END