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REM This program lists all primes no larger than an integer input by the user.
REM These primes are printed to a file. A function subprogram determines
REM whether an integer is prime.
DECLARE FUNCTION which$ (N%)
CLS
OPEN "list.bas" FOR OUTPUT AS #1
INPUT "Please enter a positive integer : ", N%
PRINT #1, "Here are the prime numbers no larger than "; N%; " :"
PRINT #1,
count = 0
FOR M% = 2 TO N%
IF which(M%) = "prime" THEN
PRINT #1, TAB(1 + 10 * (count MOD 8)); M%;
count = count + 1
END IF
NEXT M%
PRINT "There are "; count; "prime numbers no larger than"; N%; "."
PRINT "To see the list, open the file 'list.bas'."
END
FUNCTION which$ (N%)
which = "prime"
IF N% = 1 THEN which = "not prime"
M = INT(SQR(N%))
FOR I = 2 TO M
IF N% MOD I = 0 THEN which = "not prime"
NEXT I
END FUNCTION
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