'*********************************************
'*    Factorization of an integer number     *
'* ----------------------------------------- *
'* Sample run:                               *
'*                                           *
'* ? 394616                                  *
'*                                           *
'* 2 2 2 107 461                             *
'*                                           *
'* ----------------------------------------- *
'* Ref.: "Mathématiques par l'informatique   *
'*        individuelle (1) By H. Lehning     *
'*        et D. Jakubowicz, Masson, Paris,   *
'*        1982" [BIBLI 06].                  *
'*********************************************
'Enter integer number to be factorized
cls
print
input " ? ", N
print
'Test if multiple of 2
50 D=N-2*INT(N/2)
if D=0 then print 2; : N=N/2 : goto 50
'Test if multiple of 3
100 D=N-3*INT(N/3)
if D=0 then print 3; : N=N/3 : goto 100
'Test of divisors 6i-1 and 6i+1 up to sqr(N)
'Prime numbers are of the form 6i-1 or 6i+1
for i%=6 to sqr(N)+1 step 6
150 D=N-(i%-1)*INT(N/(i%-1))
  if D=0 then print i%-1; : N=N/(i%-1) : goto 150
200 D=N-(i%+1)*INT(N/(i%+1))
  if D=0 then print i%+1; : N=N/(i%+1) : goto 200
next i%
if N>1 then print N
end

'end of file factors.bas