Contents

About This Guide

The eBidyaloy SC-991BF is an on-screen scientific calculator emulator for classrooms and study — available on Windows, macOS, Web, Android and iOS. It reproduces a modern ClassWiz-style scientific calculator: a natural “textbook” display, 13 calculator apps, physical constants, unit conversions, and a live step-by-step explainer for teaching.

How to read the key operations

Key presses are shown as chips, e.g. 7 × 8 EXE. A key’s SHIFT function (orange label above the key) is written SHIFT then the key; a VARIABLE letter (gold) is entered from the VARIABLE menu.

Keys & Key Markings

The SC-991BF keypad is arranged in the same zones as a modern scientific calculator: a title strip, the LCD, a control cluster, five soft keys, two scientific rows, and the number pad.

Key Markings — three functions per key

Control Cluster

Soft Keys

Scientific Keys

Number Pad

Menu-Operation Shorthand

To keep instructions short, this guide writes menu paths in a compact form. For example:

…is the same as the full operation:

Entering & Editing Calculations

The SC-991BF uses a natural textbook display (MathI/MathO): fractions, roots, powers and other expressions appear on screen just as they are written on paper. You type an expression from left to right and press EXE to evaluate it.

Keys such as ▢∕▢ (fraction), √▢ (root) and ▢^ (power) insert an empty template with boxes to fill. Type into the highlighted box, and press ▶ to move out of it and continue the calculation.

Moving the cursor

Use the arrow keys to move the flashing cursor through an expression without erasing anything:

Deleting and inserting

To correct a mistake, move the cursor to the spot and use:

Correcting after a result

After you press EXE and see a result, you have two choices:

• Begin a new calculation — just start typing, and the previous entry is cleared.
• Edit the previous entry — press ◀ or ▶ to bring the expression back with the cursor in it, change what you need, and press EXE again.

The calculator keeps your last 30 calculations. From a result, press ▲ to step back through previous entries and ▼ to step forward. A recalled entry can be re-used in two ways:

• Press EXE to re-run the recalled calculation as it is.
• Move the cursor into it, edit the expression, then press EXE to evaluate the changed version.

Reusing the last answer with Ans

The result of the most recent calculation is held in Ans. Start a new calculation with an operator (for example + or ×) and the calculator inserts Ans automatically, or press Ans to use it anywhere in an expression.

Using Menus & Settings

Many operations use menu screens. Press ⚙ while using a calculator app to open the SETTINGS menu shown below. Each item with a ▸ opens a further menu.

The SETTINGS menu has two groups: Calc Settings (how calculations behave and display) and Reset. Drill in with OK; each setting shows a numbered list of options to choose from.

Calc Settings

Reset

Using the CATALOG

Press CATALOG to open a scrollable list of the commands, functions and symbols available in the current app. Move the highlight with ▲ ▼ and press OK to insert the selected item; press ↺ to close.

CATALOG commands

CONST ▸ opens a menu of 47 scientific constants (CODATA-2022) organised into six categories. Choose a category, then a constant, to insert its symbol and value into your calculation.

CONV ▸ applies a unit conversion to the value currently on the display. First compute a value, then choose a category and a conversion; the result is replaced by the converted value.

Example — greatest common divisor from CATALOG

To compute the GCD of 12 and 18:

Calculator Apps

Press ⌂ to display the HOME screen — the menu of all installed calculator apps. Use ▲ ▼ ◀ ▶ to move the highlight to an app, then press OK. Alternatively, press the number key shown on an app’s icon (its option number) to open it directly.

When you open an app you see either a calculation screen or a short menu to choose the calculation type. Each app is documented in full — every function with worked examples — in the chapters that follow.

Extended Display & Explainer

When teaching with the SC-991BF on a large screen, open the extended display with the ⧉ (cast) button in the title bar. A greatly enlarged copy of the calculator’s LCD appears beside the keypad so the whole class can read the current expression and result. The panel is marked LIVE DISPLAY and refreshes automatically as you type.

Below the extended display, the explainer turns any Calculate result into a lesson. It has two tabs:

• EXPLANATION — a plain-language walkthrough of what each function and operation does, in order.
• STEPS — the working shown as a reduction: the expression is rewritten one step at a time, each line a little more simplified, down to the final answer (shown in green).

Example 1 — roots and arithmetic

Example 2 — trigonometry (Degree)

Example 3 — powers

Example 4 — logarithms

Example 5 — implicit multiplication priority

Example 6 — order of operations

Calculate App Reference

The Calculate app is the calculator's main workspace. Enter an expression in natural textbook format and press EXE to evaluate it. This chapter covers every function available in Calculate, grouped by type, each with a worked example.

Basic Arithmetic & Priority

Use + − × ÷ for the four operations and ( ) to group terms. Calculations follow standard priority: functions and powers first, then × ÷, then + −. An omitted × (implicit multiplication) before a bracket or constant binds tighter than ÷.

Fractions

Press ▢∕▢ for a fraction template and SHIFT ▢∕▢ for a mixed number. Results appear as fractions; press ⇄ (FORMAT) to switch to a decimal.

Powers & Roots

▢² squares, SHIFT ▢² cubes, ▢^ raises to any power, √▢ is a square root, SHIFT √▢ a cube root, and SHIFT ▢^ gives the x-th root.

Exponential & Logarithmic

log is base-10 log, ln is natural log, SHIFT log is 10ˣ, SHIFT ln is eˣ. Use the CATALOG log▢(▢) for a logarithm to any base.

Trigonometric Functions

sin cos tan and their inverses (SHIFT + the key) use the current Angle Unit. Append ° ʳ ᵍ (from CATALOG) to give a value in a specific unit regardless of the mode.

Hyperbolic Functions

The hyperbolic functions sinh, cosh, tanh and their inverses are on the CATALOG menu.

Percentage

Enter a value followed by SHIFT ( (the % operator). A percentage is interpreted as “per hundred”.

Permutation, Combination & Factorial

SHIFT × is nPr, SHIFT ÷ is nCr, and x! (factorial) is on the CATALOG menu.

Numeric Functions

The CATALOG provides Abs (absolute value), Int (truncate), Frac (fractional part), Intg (floor), Rnd (round to the display) and x⁻¹ (reciprocal).

GCD, LCM & Random

From the CATALOG: GCD(, LCM(, RanInt#( (a random integer in a range) and Ran# (a random number in [0, 1)).

Calculus — Derivative & Integral

The CATALOG offers d/dx (numerical derivative at a point) and ∫dx (definite integral between limits).

Summation & Product

Σ sums and Π multiplies an expression as a counter runs from a lower to an upper limit.

SOLVE, CALC & VERIFY

SOLVE finds a root of f(x) = 0 by Newton's method. CALC evaluates an expression after prompting for each variable. VERIFY tests whether a relation (=, ≠, <, >, ≤, ≥) is true.

Coordinate Conversion

Pol( converts rectangular (x, y) to polar (r, θ); Rec( converts polar (r, θ) back to rectangular (x, y). Both are on the CATALOG.

Variables, Ans & Constants

Store a result into A–F, x, y, z or M with the VARIABLE menu, and recall it later. Ans reuses the previous answer; SHIFT 7/8 insert π and e. Physical constants come from CATALOG → CONST ▸.

Result Formats & Tools

After a result, ⇄ (FORMAT / S⇔D) toggles exact ⇄ decimal, and the TOOLS menu offers Prime Factor, Recurring Decimal, Sexagesimal and Improper Fraction. The CATALOG adds ENG (engineering form) and FACT.

Statistics App Reference

The Statistics app summarises a set of data and fits regression models. You type values into a list, then read off statistics such as the mean, standard deviation and quartiles; for paired data it also finds the line or curve of best fit. Open it from HOME by pointing to Statistics and pressing OK.

Choosing an analysis type

Entering data

Type a value and press EXE to drop to the next row. Move with the arrow keys, overwrite a cell by typing over it, and delete a value with DEL. To weight values by how often they occur, turn on the Frequency column from ⚙ → Statistics ▸ Frequency ▸ On.

1-Variable statistics

Enter the data with:

Normal distribution from 1-variable data

On the 1-variable result screen, press EXE to open the Norm-Dist tools. They convert a data value x to a probability using the fitted mean and σ: P(t) is the lower-tail area Φ(t), Q(t) = Φ(t) − 0.5, R(t) = 1 − Φ(t), and ▸t standardises x into t = (x − x̄) / σₓ.

Two-variable regression

Choose a 2-variable model to get an x and a y column. Enter each pair, then press FUNCTION for the fitted coefficients and the correlation r.

Statistics calculation screen

Distribution App Reference

The Distribution app evaluates the common probability distributions. Choose a distribution from the menu, enter its parameters, and read the probability — or, for the list distributions, a whole table of probabilities.

Choosing a distribution

Normal distribution

Binomial distribution (list input)

Enter N (trials) and p (success probability) once, then a growable list of x values; a probability is returned for each. PD gives P(X = x); CD gives P(X ≤ x).

Poisson distribution (list input)

Table App Reference

The Table app tabulates one or two functions over a range of x — ideal for plotting points, spotting where a function crosses zero, and comparing two functions side by side.

Defining the function(s) and range

Type the formula for f(x) using the x key for the variable. To tabulate a second function, turn on g(x) from ⚙ → Table ▸ f(x)/g(x). The calculator then asks for Start, End and Step and builds a row for each x (up to 45 rows).

Enter the function with:

Equation App Reference

The Equation app solves two kinds of problem: simultaneous linear systems with 2, 3 or 4 unknowns, and polynomial equations of degree 2, 3 or 4. You enter only the coefficients and the calculator returns the complete solution set.

Choosing an equation type

Simultaneous equations

Each row of the grid is one equation. For 2 unknowns the columns are x, y and the constant =. Enter the coefficients left to right, pressing EXE after each.

Key operation:

Polynomial equations

Enter the coefficients from the highest power down. The quadratic x² − 5x + 6 = 0 uses a = 1, b = −5, c = 6.

Complex roots

When a polynomial has non-real roots, the Equation Complex Roots setting decides whether they are shown. It is Off by default (only real roots appear). Turn it on from SETTINGS → Equation Complex Roots ▸ On.

Inequality App Reference

The Inequality app solves a polynomial inequality and reports the solution as a set of intervals on the number line. It handles quadratic, cubic and quartic inequalities against 0.

Choosing degree and direction

Complex App Reference

The Complex app performs the four operations on two complex numbers z₁ = a + bi and z₂ = c + di, and can show the result in rectangular (a + bi) or polar (r∠θ) form. The imaginary unit i satisfies i² = −1.

Selecting the operation

Polar form and complex functions

Set Complex Result ▸ r∠θ in SETTINGS to read a result in polar form. The FUNCTION menu inside the app also offers Abs (modulus |z|), arg (argument), Conjg (conjugate z̄), ReP (real part) and ImP (imaginary part).

Base-N App Reference

The Base-N app works with whole numbers in four bases — DEC (10), HEX (16), OCT (8) and BIN (2) — and includes the bitwise logic operators. All arithmetic is integer arithmetic on a 32-bit two's-complement value.

Switching base

The active base is shown at the top of the screen. Press the base soft keys DEC, HEX, OCT, BIN to re-display the current value in another base — the value never changes, only its notation.

Bitwise logic operators

Press CATALOG in Base-N to insert a logic operator: and, or, xor, xnor, not and Neg (two's-complement negate). These operate on the binary bit patterns.

Negative values

Decimal shows a signed value; the other bases show the 32-bit two's-complement bit pattern, so a negative number prints as its unsigned pattern.

Matrix App Reference

The Matrix app performs calculations with matrices of up to four rows and four columns (and rectangular m×n matrices). You store values in the matrix memories MatA, MatB, MatC and MatD, then build an expression from them. The result of every matrix calculation is retained in a special memory called MatAns, which you can feed straight into the next calculation.

Creating and entering a matrix

When you open an operation, the calculator first asks for the dimensions (rows × columns), then shows an empty grid. Fill it cell by cell, pressing EXE after each value to advance to the next cell. This grid holds MatA = 2111:

Addition and Subtraction

Multiplication

Powers — Square and Cube

A square matrix can be raised to a power. MatA² means MatA × MatA, and MatA³ means MatA × MatA × MatA.

Inverse

The inverse MatA⁻¹ is the matrix that satisfies MatA × MatA⁻¹ = I (the identity). It exists only for a square matrix whose determinant is non-zero.

Determinant

The determinant is a single number describing a square matrix. For 1×1, 2×2 and 3×3 matrices it is computed as:

Transpose

The transpose Mᵀ turns rows into columns. It works for any matrix, including rectangular ones.

Identity Matrix

Identity(n) creates the n×n identity matrix — 1s on the main diagonal and 0s everywhere else. Multiplying any matrix by the identity leaves it unchanged.

Vector App Reference

The Vector app stores two vectors, VctA and VctB, in 2 or 3 dimensions and computes their sum, difference, dot product, cross product, magnitudes, the angle between them and their unit vectors.

Choosing dimensions

Key operation:

Ratio App Reference

The Ratio app finds the missing term X in a proportion A : B = C : D. Choose which position is unknown, enter the three known values, and the calculator solves for X by cross-multiplication.

Choosing the form

Key operation:

Spreadsheet App Reference

The Spreadsheet app is a grid of 5 columns (A–E) × 45 rows. Each cell holds either a number or a formula that begins with = and may reference other cells (A1, B2, …). Formulas recalculate automatically as you edit.

Entering constants

Move the cursor with the arrow keys and type a number to enter a constant into a cell. Press EXE to confirm and drop to the next row. The examples in this chapter build on column A holding the values 1 to 5.

Entering formulas

Start a cell with = to make it a formula. A formula may contain numbers, operators and cell references (A1, B2, …). A reference always tracks the current value of that cell, so the formula recalculates automatically whenever the referenced cell changes.

Relative and absolute references

When a formula is copied or filled to another cell, its references shift with it — these are relative references. A $ locks part of a reference so it does not shift: $A$1 is fully locked, A$1 locks only the row and $A1 only the column.

Range commands — Sum, Min, Max, Mean

The commands Sum(, Min(, Max( and Mean( operate over a block of cells written as a range such as A1:A5. Insert them from the SHEET commands in the CATALOG.

The spreadsheet TOOLS menu

Press TOOLS inside the sheet for editing commands that act on the pointed cell or range:

Math Box App Reference

The Math Box app is a set of interactive learning aids: probability experiments and visual number tools. Choose a tool from the menu.

The Math Box menu

Constants & Unit Conversions

The CONST ▸ sub-menu inserts any of these 47 scientific constants (CODATA-based values) into a calculation. Point to a category, then to a constant, and press OK to insert its symbol and value. The six categories and their constants are:

Universal

Electromagnetic

Atomic & Nuclear

Physico-Chem

Adopted Values

Other

The CONV ▸ sub-menu converts the value currently on the display. First compute or type a value, then choose a category and a conversion; the display is replaced by the converted value. There are 40 conversions in nine categories:

Length

Area

Volume

Mass

Velocity

Pressure

Energy

Power

Temperature

Technical Reference

The calculator evaluates an expression according to a fixed priority sequence. Basically, calculations run from left to right, expressions inside parentheses have the highest priority, and each command has the priority shown below.

Precautions when a calculation contains negative values

Because a postfix function such as x² (priority 3) binds tighter than the negative sign (priority 4), a leading minus applies to the whole power. To square a negative value you must enclose it in parentheses.

The SC-991BF emulator performs every calculation in IEEE-754 double precision — the same arithmetic used throughout modern computing — and then formats the answer the way a scientific calculator would.

Function input ranges

The following table lists the practical input range of the main functions. Values outside a range give a Math ERROR.

When a calculation cannot be completed, the calculator shows an error message instead of a result. Press ◀ or ▶ to return to the expression with the cursor at the position of the problem, correct it, and try again. The common messages are:

Frequently Asked Questions