Source code in the basic programming language

10 DEF FN MOD(A) = INT((A / B - INT(A / B)) * B + .05) * SGN(A / B)
20 INPUT"M=";M%
30 INPUT"N=";N%
40 GOSUB 100
50 PRINT R
60 END

100 REM LEAST COMMON MULTIPLE M% N%
110 R = 0
120 IF M% = 0 OR N% = 0 THEN RETURN
130 A% = M% : B% = N% : GOSUB 200"GCD
140 R = ABS(M%*N%)/R
150 RETURN

200 REM GCD ITERATIVE EUCLID A% B%
210 FOR B = B% TO 0 STEP 0
220     C% = A%
230     A% = B
240     B = FN MOD(C%)
250 NEXT B
260 R = ABS(A%)
270 RETURN

      DEF FN_LCM(M%,N%)
      IF M%=0 OR N%=0 THEN =0 ELSE =ABS(M%*N%)/FN_GCD_Iterative_Euclid(M%, N%)
      
      DEF FN_GCD_Iterative_Euclid(A%, B%)
      LOCAL C%
      WHILE B%
        C% = A%
        A% = B%
        B% = C% MOD B%
      ENDWHILE
      = ABS(A%)

100 DEF LCM(A,B)=(A*B)/GCD(A,B)
110 DEF GCD(A,B)
120   DO WHILE B>0
130     LET T=B:LET B=MOD(A,B):LET A=T
140   LOOP 
150   LET GCD=A
160 END DEF 
170 PRINT LCM(12,18)

10 PRINT "First number"
20 INPUT A
30 PRINT "Second number"
40 INPUT B
42 LET Q = A
44 LET R = B
50 IF Q<0 THEN LET Q=-Q
60 IF R<0 THEN LET R=-R
70 IF Q>R THEN GOTO 130
80 LET R = R - Q
90 IF Q=0 THEN GOTO 110
100 GOTO 50
110 LET U = (A*B)/R
111 IF U < 0 THEN LET U = - U
112 PRINT U
120 END
130 LET C=Q
140 LET Q=R
150 LET R=C
160 GOTO 70