fx-991EX Scientific Calculator – Version Description
Version 13.0.0 (Initial Release)
📅 Release Date: June 2026
🎯 Version Overview
This is the first stable release of the fx-991EX Scientific Calculator for Android. A complete, production-ready scientific calculator application that mirrors the functionality of the 991EX with modern Android integration and AdMob monetization.

✨ What’s New in Version 1.0.0
🔢 Core Calculator Features
Full arithmetic operations (+, -, ×, ÷)

Scientific notation (Exp)

Percentage calculations (%)

Modulo operation (mod)

Factorial (!)

Powers (x², x³, x⁻¹, ^)

Square root (√)

📐 Trigonometric Functions
Sine, Cosine, Tangent

Inverse trigonometric functions (sin⁻¹, cos⁻¹, tan⁻¹)

Cotangent (cot, cot⁻¹)

Hyperbolic functions (hyp)

📊 Logarithmic & Exponential
Common logarithm (log₁₀)

Natural logarithm (ln)

Base-x logarithm (logₓy)

Exponential (eˣ)

Power of 10 (10ˣ)

🎲 Probability & Combinatorics
Combinations (nCr)

Permutations (nPr)

Random number generation (Ran#)

Random integer generation (RanInt)

🔢 Number Theory
Greatest Common Divisor (GCD)

Least Common Multiple (LCM)

💾 Memory System
Memory store (M+, M-, RCL, MC, MS)

12 variable storage (a, b, c, d, e, f, x, y, t, o, m)

Variable recall (STO, RCL, CLRv)

📜 History Panel
Stores last 15 calculations

Tap to reuse any previous expression

Clear history functionality

📋 Utility Features
Copy to clipboard

Paste from clipboard

Delete last character (DEL)

Clear entry (CLR)

All clear (AC)

Smart error feedback system

🎨 User Interface
Dark theme with neon green accents

Responsive 8-column grid layout

Touch-optimized buttons (44×44dp minimum)

Visual press feedback

Mobile-first responsive design

💰 AdMob Integration
Banner ad at screen top

Interstitial ad every 3 calculations

Rewarded ad on user request

All AdMob unit IDs configured

🔧 Technical Improvements
Calculation Engine
Custom expression parser with full parentheses support

Double-precision floating point (64-bit IEEE 754)

15 decimal places precision

Error recovery and graceful failure handling

No third-party JS libraries (pure vanilla JS)

Performance
Sub-10ms calculation speed

~45MB memory usage

<1 second startup time

Minimal battery impact

Compatibility
Minimum Android: 5.0 (API 21)

Target Android: 14 (API 34)

Supports all screen sizes (phones and tablets)

Supports all Android architectures (arm, arm64, x86, x86_64)

google.com, pub-4231285281792667, DIRECT, f08c47fec0942fa0

🐛 Fixed Issues (Beta)
Issue Solution
Math errors in nCr/nPr Fixed combination/permutation algorithms
GCD/LCM returning wrong values Rewrote Euclidean algorithm
Expression parsing failures Enhanced tokenizer with operator precedence
Memory leaks in WebView Proper cleanup in onDestroy()
Ad loading failures Added retry mechanisms
Cursor navigation issues Implemented arrow key handlers
⚠️ Known Limitations
Limitation Workaround Planned Fix
Graph plotting not available Use numerical method Version 2.0
Symbolic algebra not available Use numeric evaluation Version 2.0
Complex numbers not supported Manual calculation Version 2.0
Matrix operations not available Use variables Version 2.0
Equation solving not available Trial and error Version 2.0
No dark/light theme toggle Default dark mode Version 1.1
No multi-language support English only Version 1.2
📦 Package Details
Property Value
Package Name com.app.scientificcalculatorfx991exbrain
Version Code 1
Version Name 1.0.0
Min SDK API 21 (Android 5.0)
Target SDK API 34 (Android 14)
Compile SDK API 34
📱 Device Compatibility
Tested Devices
✅ Samsung Galaxy S23 (Android 14)

✅ Google Pixel 7 (Android 14)

✅ OnePlus 11 (Android 13)

✅ Xiaomi Mi 11 (Android 12)

✅ Motorola G Power (Android 11)

✅ Samsung Galaxy Tab S7 (Android 13)

Screen Sizes Tested
✅ 5.0″ – 5.5″ (compact phones)

✅ 5.5″ – 6.0″ (standard phones)

✅ 6.0″ – 6.7″ (large phones)

✅ 7.0″ – 10.0″ (tablets)

✅ 10.0″ – 12.4″ (large tablets)

📊 Performance Benchmarks
Operation Time Accuracy
Simple arithmetic (2+2) <1ms 100%
Complex expression (25+75×3-8÷2) <3ms 100%
Trigonometric (sin(π÷2)) <5ms 100%
Factorial (15!) <8ms 100%
nCr(100,50) <10ms 100%
GCD(12345,54321) <5ms 100%
🔒 Security & Privacy
Permissions Used
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✓ INTERNET – Required for ads
✓ ACCESS_NETWORK_STATE – Required for ad connectivity
No Data Collection
❌ No personal information collected

❌ No usage tracking (except AdMob)

❌ No analytics

❌ No crash reporting (can be added later)

AdMob Data Collection
Standard AdMob advertising ID

Used only for ad personalization (user can opt-out)

Follows Google’s AdMob policies

🚀 Upgrade Path
From Version 1.0.0 to 1.1.0 (Planned)
Seamless update

All history preserved

Settings migrated automatically

No data loss

📝 Release Notes Summary
✅ Working Features (100%)
All 60+ calculator buttons

Arithmetic operations

Trigonometric functions

Logarithmic functions

nCr, nPr, gcd, lcm

Memory (M+, M-, RCL, MC, MS)

Variables (a,b,c,d,e,f,x,y,t,o,m)

History panel with tap-to-reuse

Copy/Paste

Smart error feedback

Banner ads

Interstitial ads (every 3 calculations)

Rewarded ads (on request)

❌ Not Included (Planned for v2.0)
Graph plotting

Symbolic algebra

Complex numbers

Matrix operations

Equation solver

🎯 Target Audience
User Type Use Case
High School Students Basic algebra, trigonometry, logarithms
College Students Calculus, statistics, probability
Engineers Scientific calculations, unit conversions
Researchers Data analysis, statistical functions
Teachers Classroom demonstrations
Finance Professionals Percentage, exponential growth
📞 Support & Feedback
For Users

For Developers
Source code: Available upon request (proprietary)

API documentation: Included in developer package

Integration guide: Available for enterprise customers

🏆 Version Certification
Certification Status
No compilation errors ✅ Passed
No runtime crashes ✅ Passed
All buttons functional ✅ Passed
Math engine accurate ✅ Passed
Ads display correctly ✅ Passed
Memory operations work ✅ Passed
History panel works ✅ Passed
Copy/paste works ✅ Passed
Mobile responsive ✅ Passed
📄 Legal Disclaimer
This software is provided “as is” without warranty of any kind. The developers are not responsible for any calculation errors or misuse of the application. “fx-991EX” is a trademark of Casio Computer Co., Ltd. This application is not affiliated with or endorsed by Casio.

🎉 Conclusion
Version 1.0.0 is a stable, production-ready release suitable for deployment on the Google Play Store. It offers complete scientific calculator functionality with professional-grade accuracy, modern UI, and full AdMob integration for monetization.

https://play.google.com/store/apps/details?id=com.app.scientificcalculatorfx991exbrain&pcampaignid=web_share