The work area for calculations in iCALCULA is the STACK. The stack consists of four storage locations, called registers, which are "stacked" on top of each other. These registers — labeled x, y, z, and t — store and manipulate four current numerical quantities. The "oldest" quantity is stored in the t - (top) register. The most "recent" quantity is stored in the x-register. Functions and binary operators feed from x and, when necessary, y-registers and return results back to x-register.
Every register consists of two parts and, eventually, a pointer to a list.
A real number will occupy part1; part 2 will be null in this case.
A fraction will occupy part1 for the numerator and part2 for the denominator.
A complex number will occupy part1 for the real component or absolute value and part2 for the imaginary component or argument.
A vector will be described with a list of its components. Part1 and part2 will be null.
A matrix will be described with a list containing successive rows. Each element of the list - each row - points to a list with the elements of the row.
At the top of iCALCULA's screen view you can see x, y, z and t-registers. When both part1 and part2 are of interest, a part-display-button is visible at the left of the number indicating which part is being displayed. Successive touches exchange displayed part of the number:
With cartesian notation activated, part1 contains the real part of a complex number -with label Re- and part2 contains the imaginary part -with label Im-. With polar notation activated, part1 contains the modulus of the complex number - with label R- and part2 contains the argument -with label θ-.
Part1 of a fraction contains its numerator -with label N/- and part2 contains its denominator -with label /D-
If x or y - registers point to a vector, part1 and part2 will be null, and a message will be displayed indicating the number of rows of the vector. The ⇣ button - at the left of the message - will open a list representation of the data when touched.
In the same way, if x or y-registers point to a matrix, part2 and part2 will be null, and a message will be displayed indicating the number of rows and columns of the matrix. The ⇣ button will open a double list representation of the data.
When an integer is displayed in binary base a button is displayed at its left with label "FV". This button shows a full display view of the number.
If a register contains a quantity with a specific physical unit, corresponding label will be displayed at the right of the number. If bases notation is activated, a label at the right of the number will indicate represented basis.
|STACK| key gives you access to a menu with several functions that control the stack. "Stack UP" and "Stack DOWN" cycle the content of the four stack registers upwards or downwards. "Last x" restores the content of x-register to the value before last operation. You can also exchange the content of x and y-registers, and clear the content of the four registers.
During numeric input mode, an underscore "_" follows the displayed number. and indicates where the next digit will go. The underscore disappears when entry has been terminated. You exit input mode with |ENTER| key. A function or an operator key also ends numeric input.
Numbers with explicit powers of ten (such as 2.7x10³) are entered and displayed with an "E" preceding the exponent of 10 (2.7E3).
The |±| key changes the global sign of the input. This change affects only the mantissa. If you want to enter a negative exponent of 10, you must key |±| immediately before the exponent.
If your are entering a complex number in cartesian mode, the |i| key changes input from real part (part1) to imaginary part (part2). If polar mode is activated, |θ| key changes input from modulus (part1) to argument (part2).
If you are entering a fraction, the |Frac| key changes input from numerator (part1) to denominator (part2). You can enter a fraction through a decimal number with period notation. 1.23333... is written as 1.2p3. Period symbol "p" is introduced by pressing decimal point button. When you ENTER a number with period notation it is converted to fractional notation (37/30).
While you are in input mode, |⬅︎| key deletes the last entered digit. If you want to clear x-register, you must use |C| key instead.
There are several symbols that can be shown on the top of the display:
Default angle input mode. You can change the mode of entering angle quantities. |SYS| key enters a menu where you can select radian or degree input mode. An anunciator RAD or DEG indicates the angle input mode.
Complex number representation. In |SYS| menu you can set cartesian or polar form as complex number default input mode. An anunciator CARTESIAN or POLAR indicates the complex display form.
With vector input mode activated, an annunciator VECTOR is visible.
With matrix input mode activated, an annunciator MATRIX is visible.