Source code in the bcpl programming language

GET "libhdr"

LET sumdiv(n, d) = VALOF {
    LET m = n/d
    RESULTIS m*(m + 1)/2 * d
}

LET sum3or5(n) = sumdiv(n, 3) + sumdiv(n, 5) - sumdiv(n, 15)

LET start() = VALOF {
    LET sum = 0
    LET n = 1

    FOR k = 1 TO 999 DO
        IF k MOD 3 = 0 | k MOD 5 = 0 THEN sum +:= k
    writef("The sum of the multiples of 3 and 5 < 1000 is %d *n", sum)

    writef("Next, the awesome power of inclusion/exclusion...*n");
    FOR i = 1 TO 10 {
        writef("%11d %d *n", n, sum3or5(n - 1))
        n *:= 10
    }

    RESULTIS 0
}