Gw basicCode for prime numbers

Answer 1

10 REM I believe this program will do what you want, but bear in mind that

20 REM I don't have GWBASIC and haven't used it in years, so I'm going by

30 REM memory and human error checking alone. There may be typos and

40 REM the like. This program finds up to MAXPRIMES prime numbers and

50 REM stores them in the array PRIME. It's then dumped out on the screen.

60 REM Enjoy!

70 REM

100 DEFINT A-Z

110 MAXPRIMES=1000:NUMPRIMES=2

120 DIM PRIME(1000)

130 PRIME(0) = 2:PRIME(1) = 3

140 CURRENTNUM = 5

150 WHILE(NUMPRIMES < MAXPRIMES)

160 TESTNUMBER = CURRENTNUM

170 GOSUB 1010

180 IF ISPRIME = 1THEN

190 PRIME(NUMPRIMES) = CURRENTNUM

200 NUMPRIMES = NUMPRIMES + 1

210 END IF

220 REM -- take advantage of the fact that all primes greater than

230 REM -- three are one away from a multiple of six

240 IF (CURRENTNUM + 1) MOD 6 = 0 THEN

250 CURRENTNUM = CURRENTNUM + 2

260 ELSE

270 CURRENTNUM = CURRENTNUM + 4

280 END IF

290 WEND

300 REM =============

992 REM

1000 REM A Subroutine to see if the number TESTNUMBER is prime

1010 N = 0

1020 ISPRIME = 1

1030 WHILE ISPRIME = 1 AND N < NUMPRIMES AND PRIME(N) * PRIME(N) <= TESTNUMBER

1040 IF TESTNUMBER MOD PRIME(N) = 0 THEN ISPPRIME = 0

1050 N = N + 1

1060 WEND

1070 RETURN