10 'HCFACTOR  ----GWBasic or QBasic
20 'hh ----  Oct/85
30 GOTO 200
80 '
90 DEFDBL M-Y
100 C = C + 1: P = N
110 N = M - N * INT(M / N)
120 M = P
130 IF N = 0 THEN RETURN
140 GOSUB 100
150 RETURN
199 '
200 X$ = "                                                                               "
210 KEY OFF: CLS
220 LOCATE 2, 20: PRINT "** HIGHEST COMMON FACTOR **"
230 LOCATE 3, 20: PRINT "***************************"
240 PRINT : PRINT "This program uses a recursive sub-routine to find the Highest"
250 PRINT "Common Factor of 2 integers using a method credited to Euclid."
255 PRINT "Enter 0,0 to end."
260 PRINT : PRINT "Enter 2 integers of up to 25 (total) digits separated by a commma"
265 LOCATE 12, 10: INPUT X, Y
270 M = X: N = Y: C = 0: IF X = 0 THEN 400
280 GOSUB 100
285 LOCATE 17, 1: PRINT X$: PRINT X$: PRINT X$
290 LOCATE 17, 1: PRINT "The Highest Common Factor of "; X; " & "; Y; " is "; P
300 PRINT "It required "; C; " iterations."
310 LOCATE 12, 1: PRINT X$: GOTO 265
400 CLS
405 KEY ON
410 END
420 ' This seems to work only if the total number of digits
430 ' in the 2 integers is <26.