A Comprehensive Guide to Accessing C and C++ Standard Documents

In software development, C and C++ language standard documents are essential references for understanding language specifications, resolving technical disputes, and enabling cross-platform development. However, many developers find it challenging to locate these documents online, particularly amidst numerous forum discussions and outdated links. Based on highly-rated Stack Overflow Q&A, this article systematically organizes access methods for C and C++ standard documents, providing practical guidance for developers.

Official PDF Document Acquisition Channels

Official PDF documents of C and C++ standards published by ISO/IEC typically require purchase through national standards bodies or authorized distributors. As of March 2022, the following channels offer relatively reasonable prices:

• C++20 standard (ISO/IEC 14882:2020) available from csagroup.org for approximately $165 USD
• C++17, C++14, and C++98 standards available from Standards New Zealand for approximately $65 USD
• C++11 standard available from ansi.org or Techstreet for $60 USD
• C++03 standard available from ansi.org for $30 USD
• C17/C18 standard (ISO/IEC 9899:2018) available from INCITS/ANSI for $116 USD
• C11 standard available from ansi.org for $60 USD
• C99 standard available from ansi.org for $60 USD
• C90 standard available from Standards New Zealand for approximately $65 USD

Notably, searching with "INCITS/ISO/IEC" rather than "ISO/IEC" may yield more affordable versions, as INCITS (International Committee for Information Technology Standards) editions often have lower prices while containing identical content.

Free Draft Resource Access

For developers with limited budgets, draft documents released by standards committees serve as important free alternatives. Although these drafts are not the final approved standards, they are typically very close to the official versions.

C language standard drafts can be obtained through the WG14 (C Standard Committee) website:

• C99: N1256 draft (PDF link)
• C11: N1570 draft (PDF link)
• C17/C18: N2176 draft (accessible via Wayback Machine)
• C23: N3096 draft (latest working draft as of April 2023)

C++ language standard drafts can be obtained through the WG21 (C++ Standard Committee) website:

• C++98: ISO/IEC 14882:1998 draft
• C++03: related draft documents
• C++11: N3337 draft (PDF link)
• C++14: N4140 draft (GitHub link)
• C++17: N4659 draft (PDF link)
• C++20: N4860 draft (PDF link)
• C++23: N4950 draft (latest working draft)

The wg21.link website provides convenient short URL access, such as https://wg21.link/std11 pointing to the C++11 draft.

Non-PDF Format Online Resources

Beyond PDF formats, HTML and plain-text standard documents offer different browsing experiences:

• ISO Online Browsing Platform (https://www.iso.org/obp) offers online viewing of the latest C standard, but not downloading
• port70.net hosts HTML versions of C89, C99, C11, and C++11 drafts
• open-std.org provides HTML documents for C90 technical corrigenda

Caution is advised as non-PDF format documents may contain errors introduced during transcription or automated generation. Websites maintained by Tim Song and Eelis (such as https://timsong-cpp.github.io/cppwp/ and http://eel.is/c++draft/) convert LaTeX source to HTML using the cxxdraft-htmlgen tool, providing high-quality online browsing experiences.

Print Versions and Annotated Books

Printed standard documents can be purchased through national standards bodies and ISO, but prices are typically high. As alternatives, the following books contain standard text:

• Herb Schildt's The Annotated ANSI Standard contains C90 standard text, but the annotations contain errors
• Books published by Wiley and BSI contain C99 and C++03 standards

These books may be available at lower prices in second-hand markets, but attention should be paid to the accuracy of annotation content.

POSIX Extension Standards

The POSIX standard (IEEE 1003.1) requires compliant operating systems to provide C-standard-compliant compilers and defines a series of extensions. These extensions include:

• Special data types like off_t
• Additional headers like <aio.h>
• System functions like clock_gettime()
• Feature test macros like _POSIX_C_SOURCE

POSIX.1-2001 requires systems to provide a compiler invocation named "c99", typically implemented through wrapper scripts that add options like -std=c99. The Open Group website provides online HTML versions of POSIX standards, but search functionality may be limited.

Differences Between Drafts and Official Standards

Although draft documents are typically very close to final standards, important differences exist:

• Final Committee Draft (FCD) versions are password-protected and accessible only to committee members
• Drafts may contain errors corrected before final standard publication
• Technical corrigenda may not be included in drafts

For academic citation or formal development, official standard documents are recommended. However, for learning and general reference, draft documents serve as adequate substitutes.

Standard Maintenance on GitHub

The latest C++ standard draft is maintained as LaTeX source in a GitHub repository (https://github.com/cplusplus/draft). This enables:

• Developers to track standard evolution
• Tool developers to create custom-formatted outputs
• The community to more easily report and fix documentation errors

This open maintenance model enhances the accessibility and transparency of standard documents.

In summary, multiple avenues exist for obtaining C and C++ standard documents, ranging from expensive official PDFs to free online drafts. Developers should select appropriate resources based on specific needs: official documents for formal projects, free drafts for learning and research, and POSIX developers should additionally consult relevant extension standards. As standard maintenance becomes increasingly open, accessing these crucial documents will become more convenient in the future.