What is ISO/IEC 9899:2018-Information technology — Programming languages — C?

ISO 9899-C programming language is an international standard that specifies the programming language C. It is often referred to as “C18” or simply “C 2018.” This standard defines the syntax and semantics of the C programming language and provides guidelines for writing portable and maintainable C code.

Key aspects covered by ISO/IEC 9899:2018 include:

1. Language Syntax: It defines the basic syntax and grammar of the C programming language, including keywords, data types, operators, and control structures.
2. Standard Library: The standard includes a library of functions and macros that are available to C programmers. This library provides a wide range of functionality, including input and output, mathematical operations, memory management, and more.
3. Data Types: It defines various data types, including integers, floating-point numbers, characters, and pointers, along with their representation and behavior in C programs.
4. Memory Management: The standard specifies how memory allocation and deallocation should be performed using functions like malloc, free, and realloc.
5. Preprocessor Directives: C18 defines preprocessor directives, such as #define and #include, which are used for text manipulation before actual compilation.
6. Type Qualifiers: It introduces type qualifiers like const and volatile to specify the behavior of variables.
7. Error Handling: The standard outlines error handling mechanisms and error codes for functions in the standard library.
8. Standard Conformance: It establishes rules for C compilers to ensure that they adhere to the standard, promoting portability of C code across different platforms and compilers.
9. Extensions: While C18 defines the core C language, it allows for implementation-specific extensions that go beyond the standard. These extensions are often provided by compiler vendors to address platform-specific requirements.

Furthermore, ISO/IEC 9899:2018 is the successor to ISO/IEC 9899:2011 (commonly referred to as “C11”) and incorporates various enhancements and clarifications to the language. Programmers and compiler developers use this standard as a reference to ensure that their C code is compliant with the language specification.

It’s important to note that while ISO/IEC 9899 defines the core C language, there are also various additional standards and specifications that cover specific aspects of C, such as the POSIX standard for C libraries on Unix-like systems or the C Standard Library.

Requirements of ISO 9899-C programming language

ISO/IEC 9899:2018, which specifies the C programming language, sets forth several requirements and guidelines that must be followed to ensure compliance with the standard. These requirements cover various aspects of the language, including its syntax, semantics, and standard library.

Below are some of the key requirements of ISO/IEC 9899:2018:

1. Language Syntax and Semantics: The standard defines the syntax and semantics of the C language. It specifies the rules for writing C programs, including the use of keywords, data types, operators, and control structures. Programmers must adhere to these rules when writing C code.
2. Standard Library: ISO/IEC 9899:2018 includes a standard library of functions and macros that are available for use in C programs. Programmers must use these library functions according to their defined behavior as specified in the standard.
3. Data Types: The standard defines various data types, such as int, char, float, and double, along with their characteristics, such as their representation, size, and behavior. Programmers must use these data types correctly in their code.
4. Memory Management: ISO/IEC 9899:2018 specifies the functions and macros for dynamic memory allocation and deallocation, such as malloc, free, and realloc. Programmers must use these memory management functions correctly to avoid memory leaks and undefined behavior.
5. Preprocessor Directives: The standard defines preprocessor directives, such as #define, #include, and #ifdef, which are used for text manipulation before compilation. Programmers must follow the rules for using these directives.
6. Type Qualifiers: The standard introduces type qualifiers like const and volatile to specify the behavior of variables. Programmers must correctly apply these qualifiers to variables when necessary.

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7. Error Handling: ISO/IEC 9899:2018 provides guidelines for error handling and specifies error codes for functions in the standard library. Programmers should handle errors appropriately and make use of the provided error codes when necessary.
8. Standard Conformance: Compiler developers must ensure that their C compilers adhere to the rules and requirements set forth in ISO/IEC 9899:2018. This ensures that C code written to the standard is portable across different compilers and platforms.
9. Undefined Behavior: The standard explicitly defines certain behaviors as undefined, meaning that the outcome of code that exhibits such behavior is not specified by the standard. Programmers should avoid writing code that results in undefined behavior.
10. Conformance Testing: To demonstrate compliance with the standard, C compilers and implementations must pass conformance tests that verify their adherence to ISO/IEC 9899:2018. This helps ensure consistency in C language support across different tools.

Overall, ISO 9899-C programming language provides a comprehensive set of requirements and guidelines for the C programming language, covering language features, library functions, and best practices. Programmers and compiler developers should reference this standard to write compliant C code as well as develop conforming C compilers.

Benefits of ISO 9899-C programming language

The ISO/IEC 9899:2018 standard, which specifies the C programming language, offers several benefits to programmers, software developers, and the software industry as a whole. These benefits contribute to the reliability, portability, and maintainability of C code, and they help ensure that C remains a valuable language for a wide range of applications.

Here are some of the key benefits of ISO 9899-C programming language

• Standardization: ISO 9899-C programming language provides a standardized and well-documented specification for the C programming language. This standardization ensures consistency and predictability in how C code is written and executed across different platforms and compilers.
• Portability: Code written in accordance with ISO/IEC 9899 is highly portable. C programs that adhere to the standard can be compiled and run on various hardware and software platforms without modification, reducing the effort required to support multiple environments.
• Longevity: C has a long history and has remained relevant for several decades. ISO/IEC 9899:2018 ensures that C remains a stable and viable programming language, allowing organizations to continue maintaining and evolving legacy C codebases.
• Efficiency: C is known for its low-level control over hardware resources, making it suitable for systems programming, embedded systems, and performance-critical applications. The standardization provided by ISO/IEC 9899 ensures that programmers can write efficient code that takes full advantage of the hardware.

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• Interoperability: C is often used as a common language for interfacing with other programming languages like C++, Python, and Rust. ISO/IEC 9899 helps ensure smooth interoperability between C and other languages.
• Extensibility: While ISO/IEC 9899 defines the core C language, it allows for implementation-specific extensions. This flexibility allows compiler vendors to address platform-specific requirements and innovate while still adhering to the standard.
• Community and Ecosystem: C has a large and active community of developers and a rich ecosystem of libraries and tools. ISO/IEC 9899 helps maintain a cohesive and well-supported C ecosystem, making it easier for programmers to find resources and solutions.
• Legacy Code Maintenance: Many critical systems and applications are written in C. The standard ensures that legacy C code can be maintained and updated over time with confidence in its correctness and behavior.
• Teaching and Education: ISO/IEC 9899 serves as a foundation for teaching programming and computer science concepts. Its well-defined syntax and semantics make it an excellent language for introducing students to programming principles.
• Industrial and Safety-Critical Applications: C is often used in safety-critical systems like aviation, automotive, and medical devices. The standardization provided by ISO/IEC 9899 helps ensure the reliability as well as safety of software in such applications.

In summary, ISO/IEC 9899:2018 plays a crucial role in maintaining and advancing the C programming language. Its benefits include standardization, portability, efficiency, and long-term viability, making C a valuable choice for various software development scenarios.

Who needs ISO 9899-C programming language?

ISO 9899-C programming language specifies the C programming language, is relevant to a wide range of individuals, organizations, and industries.

Here are some of the key stakeholders who can benefit from or need to consider this standard:

• Programmers and Developers: C programmers are the primary users of ISO/IEC 9899:2018. They need to be familiar with the standard to write portable, maintainable, and reliable C code. Understanding the language’s syntax, semantics, and library functions is essential for developers working on C-based projects.
• Software Development Organizations: Organizations that develop software using the C programming language, especially those involved in systems programming, embedded systems, and low-level software, need to adhere to ISO/IEC 9899:2018 to ensure code quality, portability, and long-term maintainability.
• Compiler Developers: Companies and individuals responsible for developing C compilers must adhere to the standard to ensure that their compilers produce code that conforms to ISO/IEC 9899. Compiler developers use the standard as a reference to implement the C language correctly.
• Quality Assurance and Testing Teams: QA teams can use the standard to define test cases and ensure that C code complies with the language specification. This helps identify and prevent non-conforming code that may lead to unexpected behavior or security vulnerabilities.
• Educational Institutions: Schools, colleges, and universities that teach C programming courses can use ISO/IEC 9899:2018 as a foundational resource to instruct students on the correct use of the C language. It serves as a basis for curriculum development and ensuring that students learn best practices.
• Safety-Critical Industries: Industries such as aerospace, automotive, medical devices, and industrial control systems often rely on C for safety-critical software. ISO/IEC 9899:2018 helps ensure the reliability and safety of software used in these sectors.
• Standards Organizations: Organizations responsible for creating industry-specific standards may refer to ISO/IEC 9899:2018 as a foundation for software development guidelines. It provides a common reference point for compliance with coding standards in various industries.

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• Open Source and Community Projects: Many open-source projects and community-driven initiatives are written in C. Adherence to ISO/IEC 9899:2018 can help maintain consistency and quality within these projects and facilitate contributions from a diverse group of developers.
• Legacy Code Maintenance Teams: Organizations with legacy C codebases require knowledge of ISO/IEC 9899:2018 to maintain and update their existing software systems. Ensuring that legacy code complies with the standard helps preserve the code’s correctness and behavior.
• Security Professionals: Security experts and penetration testers may use the standard to identify security vulnerabilities and weaknesses in C code. Understanding the language’s behavior as defined by the standard is essential for security assessments.

In summary, ISO 9899-C programming language is relevant to anyone working with the C programming language, whether it’s for development, education, compliance, or quality assurance. It serves as a critical reference for ensuring the correctness, portability, and reliability of C code across various domains and industries.

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Also read: ISO 22301:2019 – Business Continuity Management Systems