The Casio Calculator 991 ES Plus 2nd Addition offers additional features beyond the first edition, including:

1. Advanced statistical functions: Calculate median, mode, and standard deviation.

2. Enhanced graphing capabilities: Graph equations and inequalities in 2D and 3D.

3. Symbolic algebra: Solve equations and manipulate algebraic expressions.

4. Numerical differentiation and integration: Calculate derivatives and integrals numerically.

5. Advanced trigonometry: Calculate trigonometric functions with degrees, minutes, and seconds.

6. Hyperbolic functions: Calculate hyperbolic sine, cosine, and tangent.

7. Inverse functions: Calculate inverse trigonometric and hyperbolic functions.

8. Matrix operations: Perform advanced matrix calculations, like eigenvalues and eigenvectors.

9. Vector calculations: Calculate vector dot products, cross products, and magnitudes.

10. Advanced conversions: Convert between various units, including temperature, pressure, and more.

11. Engineering and scientific notation: Perform calculations with engineering and scientific notation.

12. Complex number calculations: Calculate complex numbers with advanced operations.