Part 1: Introduction to Ada
Ada, named after Augusta Ada King-Noel, Countess of Lovelace, is a high-level programming language that was developed by the U.S. Department of Defense in the late 1970s. It was specifically designed to address the needs of critical systems, where the utmost level of reliability and robustness is required.

Part 2: Reliability and Safety
One of the key reasons behind the creation of Ada was to improve the reliability and safety of software systems. Ada’s strong static typing and compile-time checking prevent many types of runtime errors, saving programmers from potential disastrous consequences. With Ada’s exception handling mechanism, developers can gracefully manage errors and improve system resiliency.

Part 3: Efficiency and Maintainability
While focusing on reliability and safety, Ada also excels in efficiency and maintainability. The language promotes the use of modular programming and object-oriented design, making it easier to write reusable and maintainable code. With its strict compilation rules, Ada allows for efficient execution, reducing memory usage, and optimizing performance.

Part 4: Real-World Applications
Ada’s unparalleled reliability and safety features have made it a preferred choice for critical systems in various domains. It has been extensively used in aerospace, defense, transportation, and medical industries, where failure could lead to catastrophic consequences. The Mars Rover missions by NASA, air traffic control systems, and medical devices are just a few examples of the real-world applications that showcase Ada’s effectiveness.

In conclusion, Ada’s legacy as a revolutionary programming language cannot be understated. Designed to meet the stringent requirements of critical software systems, Ada stands tall in providing reliability, safety, efficiency, and maintainability. Its contribution to the industry is immense and continues to shape the way we design and develop robust software solutions. As technology advances and safety-critical systems become increasingly prevalent, Ada’s significance and influence are set to endure.