RosettaCodeData/Task/Greatest-common-divisor/IS-BASIC/greatest-common-divisor.basic

100 DEF GCD(A,B)
110   DO WHILE B>0
120     LET T=B
130     LET B=MOD(A,B)
140     LET A=T
150   LOOP
160   LET GCD=A
170 END DEF
180 PRINT GCD(12,16)