It has built-in language support for design by contract (DbC), extremely strong typing, explicit concurrency, tasks, synchronous message passing, protected objects, and non-determinism.

[11] Ada was originally designed by a team led by French computer scientist Jean Ichbiah of Honeywell under contract to the United States Department of Defense (DoD) from 1977 to 1983 to supersede over 450 programming languages used by the DoD at that time.

The Ada 95 revision, designed by S. Tucker Taft of Intermetrics between 1992 and 1995, improved support for systems, numerical, financial, and object-oriented programming (OOP).

Features of Ada include: strong typing, modular programming mechanisms (packages), run-time checking, parallel processing (tasks, synchronous message passing, protected objects, and nondeterministic select statements), exception handling, and generics.

The syntax of Ada minimizes choices of ways to perform basic operations, and prefers English keywords (such as "or else" and "and then") to symbols (such as "||" and "&&").

In the case of conditional blocks this avoids a dangling else that could pair with the wrong nested if-expression in other languages like C or Java.

For example, the syntax requires explicitly named closing of blocks to prevent errors due to mismatched end tokens.

For these reasons, Ada is sometimes used in critical systems, where any anomaly might lead to very serious consequences, e.g., accidental death, injury or severe financial loss.

Examples of systems where Ada is used include avionics, air traffic control, railways, banking, military and space technology.

[17] Though the semantics of the language allow automatic garbage collection of inaccessible objects, most implementations do not support it by default, as it would cause unpredictable behaviour in real-time systems.

In 1975, a working group, the High Order Language Working Group (HOLWG), was formed with the intent to reduce this number by finding or creating a programming language generally suitable for the department's and the UK Ministry of Defence's requirements.

After many iterations beginning with an original straw-man proposal[19] the eventual programming language was named Ada.

[20] The requirements focused on the needs of embedded computer applications, and emphasised reliability, maintainability, and efficiency.

[25] Ichbiah publicly stated that within ten years, only two programming languages would remain: Ada and Lisp.

[26] Early Ada compilers struggled to implement the large, complex language, and both compile-time and run-time performance tended to be slow and tools primitive.

[28] Several commercial companies began offering Ada compilers and associated development tools, including Alsys, TeleSoft, DDC-I, Advanced Computer Techniques, Tartan Laboratories, Irvine Compiler, TLD Systems, and Verdix.

[25] The Department of Defense Ada mandate was effectively removed in 1997, as the DoD began to embrace commercial off-the-shelf (COTS) technology.

[25] Similar requirements existed in other NATO countries: Ada was required for NATO systems involving command and control and other functions, and Ada was the mandated or preferred language for defense-related applications in countries such as Sweden, Germany, and Canada.

[26] Because of Ada's safety-critical support features, it is now used not only for military applications, but also in commercial projects where a software bug can have severe consequences, e.g., avionics and air traffic control, commercial rockets such as the Ariane 4 and 5, satellites and other space systems, railway transport and banking.

The Canadian Automated Air Traffic System was written in 1 million lines of Ada (SLOC count).

Ada is also used in other air traffic systems, e.g., the UK's next-generation Interim Future Area Control Tools Support (iFACTS) air traffic control system is designed and implemented using SPARK Ada.

[16][35] The Ada 95 revision of the language went beyond the Steelman requirements, targeting general-purpose systems in addition to embedded ones, and adding features supporting object-oriented programming.

To help with the standard revision and future acceptance, the US Air Force funded the development of the GNAT Compiler.

At the Ada-Europe 2012 conference in Stockholm, the Ada Resource Association (ARA) and Ada-Europe announced the completion of the design of the latest version of the Ada language and the submission of the reference manual to the ISO/IEC JTC 1/SC 22/WG 9 of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) for approval.

Other related standards include ISO/IEC 8651-3:1988 Information processing systems—Computer graphics—Graphical Kernel System (GKS) language bindings—Part 3: Ada.

However, Ada also has many data structuring facilities and other abstractions which were not included in the original ALGOL 60, such as type definitions, records, pointers, enumerations.

However, since Ada 2012, functions are not required to be pure and may mutate their suitably declared parameters or the global state.

Examples of common usage of compiler pragmas would be to disable certain features, such as run-time type checking or array subscript boundary checking, or to instruct the compiler to insert object code instead of a function call (as C/C++ does with inline functions).