Arithmetic Modes in Decimal BASIC

When any of following OPTION ARITHMETIC statements is written in each program unit, the program goes irrespective of the mode indicated by the toolbar icons.

Decimal            OPTION ARITHMETIC DECIMAL      (Full BASIC Compatible)
Decimal 1000-digit OPTION ARITHMETIC DECIMAL_HIGH
Binary             OPTION ARITHMETIC NATIVE       (Full BASIC Compatible)
Complex            OPTION ARITHMETIC COMPLEX
Rational           OPTION ARITHMETIC RATIONAL

Notice that OPTION statements written in the mainprogram is ineffective to external procedures.

How to select an arithmetic mode
Decimal 1000-digit mode should be used for approximated calculation in decimal fractions.
If you do not prefer approximation or you need to handle with indefinitely large integers, use the rational operation mode.
Example.
Collatz Conjecture
(If n is even, divide it by 2, if n is odd multiply it by 3 and add 1, and repeat the process indefinitely until it becomes 1.）

OPTION ARITHMETIC RATIONAL
INPUT n
DO UNTIL n=1
   IF MOD(n,2)=0 THEN 
      LET n=n/2 
   ELSE
      LET n=3*n+1
      PRINT n
   END IF
LOOP
END