How do you write a BASIC program to display whether the input number is prime or composite?

Answer 1

To write a BASIC program that checks if an input number is prime or composite, you can use a loop to test divisibility. First, prompt the user for a number and then check if it's less than 2 (which is neither prime nor composite). For numbers greater than 1, iterate from 2 to the square root of the number, checking if it divides evenly (using the modulus operator). If you find a divisor, the number is composite; otherwise, it's prime. Here's a simple example:

INPUT "Enter a number: ", N
IF N < 2 THEN PRINT "Neither prime nor composite": END
IS_PRIME = TRUE
FOR I = 2 TO SQR(N)
    IF N MOD I = 0 THEN
        IS_PRIME = FALSE
        EXIT FOR
    END IF
NEXT I
IF IS_PRIME THEN PRINT N; " is prime" ELSE PRINT N; " is composite"