A fraction is a ratio of two integers. Fractions are traditionally written “2/3” but Calc uses the notation ‘2:3’. (The / key performs RPN division; the following two sequences push the number ‘2:3’ on the stack: 2 : 3 RET, or 2 RET 3 / assuming Fraction mode has been enabled.) When the Calculator produces a fractional result it always reduces it to simplest form, which may in fact be an integer.
Fractions may also be entered in a three-part form, where ‘2:3:4’ represents two-and-three-quarters. See Fraction Formats, for fraction display formats.
Non-decimal fractions are entered and displayed as ‘radix#num:denom’ (or in the analogous three-part form). The numerator and denominator always use the same radix.