Introducció
This user manual provides comprehensive instructions for the Casio Scientific Calculator FX-991ES Plus. Designed for students and professionals, this calculator offers advanced mathematical functions and a Natural Textbook Display, allowing expressions to be entered and viewed as they appear in textbooks. It is equipped with 417 functions to support a wide range of calculations, from basic arithmetic to complex scientific and statistical operations.
The FX-991ES Plus is powered by both solar energy and a battery, ensuring reliable operation in various lighting conditions. Its robust design and intuitive interface make it a valuable tool for academic and professional use.

This image displays the Casio FX-991ES Plus scientific calculator, presented within its retail packaging. The packaging highlights key features such as 'Natural V.P.A.M.' and '417 Functions', along with a clear view of the calculator's display and keypad layout.
Configuració
Font d'alimentació
The Casio FX-991ES Plus calculator utilizes a dual power system: solar power and battery power. When sufficient light is available, the calculator operates on solar power. In low-light conditions, it automatically switches to battery power. No specific battery installation is typically required for initial use as it comes pre-installed.
Encès inicial
Per engegar la calculadora, premeu la tecla ON button located at the top right of the keypad. The display will show the initial screen, ready for calculations.

A view of the back of the Casio FX-991ES Plus scientific calculator, showing its dark blue protective slide cover. This cover helps protect the calculator when not in use.
Instruccions de funcionament
Operacions bàsiques
Perform basic arithmetic operations (+, -, ×, ÷) by entering numbers and pressing the corresponding operation keys. Press = per obtenir el resultat.
Selecció del mode
Premeu el botó MODE button to access different calculation modes. Use the arrow keys to navigate and press the corresponding number to select a mode:
- COMP (1): General calculations.
- STAT (2): Statistical calculations.
- TABLE (3): Generate a number table from a function.
- EQN (5): Equation solving (simultaneous linear equations, quadratic, cubic).
- MATRIX (6): Matrix calculations.
- VECTOR (7): Càlculs vectorials.
- CMPLX (2): Complex number calculations (when in COMP mode, press MODE then 2).
- BASE-N (4): Base-N calculations (binary, octal, decimal, hexadecimal).
Natural Textbook Display (Natural V.P.A.M.)
This feature allows input and display of fractions, roots, and other expressions as they are written in textbooks. For example, to input a fraction, use the fraction key [a b/c]. To input a square root, press [√].
Funcions científiques
Access scientific functions (e.g., sin, cos, tan, log, ln, powers, roots) by pressing the function key directly or by pressing MAJÚS followed by the desired function key for its secondary operation.
Funcions de memòria
The calculator includes independent memory (M) and variable memories (A, B, C, D, E, F, X, Y). Use STO (Botiga) i RCL (Recall) to manage values in memory.
Unit Conversions and Scientific Constants
The calculator has built-in unit conversion functions and scientific constants. Refer to the markings above the keys for specific functions, typically accessed via MAJÚS or ALFA.
Manteniment
Neteja
To clean the calculator, wipe it gently with a soft, dry cloth. Do not use abrasive cleaners, solvents, or wet cloths, as these can damage the casing o components interns.
Emmagatzematge
Store the calculator in a cool, dry place away from direct sunlight, extreme temperatures, and high humidity. Always use the protective slide cover when the calculator is not in use to prevent damage to the display and keys.
Canvi de bateria
While the calculator is primarily solar-powered, it also uses a button-cell battery for backup. If the display becomes dim or erratic in low light, the battery may need replacement. Consult a qualified technician or refer to the detailed battery replacement instructions in the full product manual if available, as improper replacement can damage the device.
Resolució de problemes
Problemes de visualització
- Pantalla en blanc: Ensure sufficient light for solar power. If in low light, the battery might be depleted.
- Pantalla atenuada: Indica poca bateria.
Missatges d'error
- Math ERROR: Occurs when a mathematical operation is invalid (e.g., division by zero, square root of a negative number). Check your input.
- Syntax ERROR: Indicates an incorrect format in the expression. Review the entered expression for proper syntax.
- Stack ERROR: Occurs when the calculation exceeds the calculator's capacity (e.g., too many nested parentheses).
Reinicialització de la calculadora
If the calculator behaves erratically, a reset may resolve the issue. Press MAJÚS aleshores CLR (9)i, a continuació, seleccioneu All (3), i confirmeu amb =. This will clear all memory and settings, returning the calculator to its factory default state.
Especificacions
| Marca | Casio |
| Nom del model | FX-991ES Plus |
| Tipus de calculadora | Scientific / Engineering |
| Font d'alimentació | Solar, bateria |
| Color | Blanc |
| Material | Plàstic |
| Pes de l'article | 180 g |
| Dimensions del paquet | 19.2 x 8.3 x 2.3 cm |
| Nombre de funcions | 417 |
| Tipus de visualització | Natural Textbook Display (Natural V.P.A.M.) |

The front of the Casio FX-991ES Plus calculator box, emphasizing its 'Natural V.P.A.M.' display and the '417 Functions' it offers. The image also shows the calculator itself, illustrating its design and the ability to enter expressions as written in textbooks.
Garantia i Suport
For information regarding product warranty, please refer to the warranty card included with your purchase or visit the official Casio website. For technical support, frequently asked questions, or further assistance, please contact Casio customer support through their official channels.
Always ensure you are using official Casio resources for support to guarantee accurate and reliable information.





