Topic: Prime program implemented in QuickBasic with protective IF-ELSE-ENDIF

February 11, 2016

PRINT "Please enter a number to see if it is a prime:"
INPUT number

prime$ = "True"

IF number < 0 OR number > 1000000 THEN

    PRINT "Number out of range."

ELSE

    IF number = 0 OR number = 1 THEN

        prime$ = "False"

    ELSE

        divisor = 2

        WHILE divisor < number

            intermediate = number

            WHILE intermediate >= divisor
                intermediate = intermediate - divisor
            WEND

            remainder = intermediate

            IF remainder = 0 THEN
                prime$ = "False"
            END IF

            divisor = divisor + 1

        WEND

    END IF

    IF print$ = "True" THEN
        PRINT number; " is a prime."
    ELSE
        PRINT number; " is not a prime."
    END IF

END IF