Fractions are stored in the memory stack using both Part1 and Part2 of the registers. If you enter an integer number and press |FRAC| instead of |ENTER| key, the integer number is stored in Part1 of x-register as numerator, display is cleared and you can continue with the input of the fraction. A blue "/D" label is displayed at the left of x-display to indicate that the denominator is being input., which will be stored in Part2. The underscore "_" indicates you are in input mode. If your press on the blue "/D" label x-display changes to Part1 (numerator) and blue label indicates "/N". Successive touches exchange displayed part of the fraction and you can continue editing its value while in input mode. You get out of input mode in the usual way: |ENTER| key or a function key.
Once x-register is labeled as a fraction (which is indicated through the "/N" or "/D" labels) operators adapt its functionality.
If x-register is a fraction, or if while in input mode a non integer number is input, |FRAC| key enters Frac menu with functions:
|Number to Fraction| : Converts x-register decimal number to the most approximate fraction having a denominator lower than "MaxDenominator" system variable.
|Fraction to Number| : Converts x-register fraction to a decimal number.
|Reduce Fraction| : Reduces x-register fraction to an equivalent with minimum numerator and denominator.
|Improper Fraction| : If numerator in x-register is greater than denominator, the improper fraction is calculated. Integer part is stored in y-register and rational part in x-register.
|x-Vec Greatest Common Denominator| : Calculates GCD of a vector of integers in x-register.
|x-Vec Lowest Common Multiple| : Calculates LCM of a vector of integers in x-register.
You can change the value of "MaxDenominator" system variable through the function |Set MaxDenominator to X| which can be found in |SYSTEM| key menu.
Following operators perform computations on fractions:
|+| : Computes (y + x)-registers and stores fraction result in x-register
|-| : Computes (y - x)-registers and stores fraction result in x-register
|×| : Computes (y * x)-registers and stores fraction result in x-register
|÷| : Computes (y / x)-registers and stores fraction result in x-register
|1/x| : Computes inverse of x-register and stores fraction result in x-register
|x²| : Computes square of x-register and stores fraction result in x-register
|y ˣ| : Computes power x-register of y-register and stores fraction result in x-register. x-register must be an integer
|±| : Changes sign to x-register