A.1 General
This appendix is a reference. It is not intended to be read from beginning to end like a chapter. It (more or
less) systematically describes key elements of the C++ language. It is not a complete reference, though; it is
just a summary. Its focus and emphasis were determined by student questions. Often, you will need to look
at the chapters for a more complete explanation. This summary does not attempt to equal the precision and
terminology of the standard. Instead, it attempts to be accessible. For more information, see Stroustrup, The
C++ Programming Language. The definition of C++ is the ISO C++ standard, but that document is neither
intended for nor suitable for novices. Don’t forget to use your online documentation. If you look at this
appendix while working on the early chapters, expect much to be “mysterious,” that is, explained in later
chapters.
For standard library facilities, see Appendix B.
The standard for C++ is defined by a committee working under the auspices of the ISO (the international
organization for standards) in collaboration with national standards bodies, such as INCITS (United States),
BSI (United Kingdom), and AFNOR (France). The current definition is ISO/IEC 14882:2011 Standard for
Programming Language C++.
A.1.1 Terminology
The C++ standard defines what a C++ program is and what the various constructs mean:
• Conforming: A program that is C++ according to the standard is called conforming (or colloquially,
legal or valid).
• Implementation defined: A program can (and usually does) depend on features (such as the size of
an int and the numeric value of 'a') that are only well defined on a given compiler, operating
system, machine architecture, etc. The implementation-defined features are listed in the standard and
must be documented in implementation documentation, and many are reflected in standard headers,
such as <limits> (see §B.1.1). So, being conforming is not the same as being portable to all C++
implementations.
• Unspecified: The meaning of some constructs is unspecified, undefined, or not conforming but not
requiring a diagnostic. Obviously, such features are best avoided. This book avoids them. The
unspecified features to avoid include
• Inconsistent definitions in separate source files (use header files consistently; see §8.3)
• Reading and writing the same variable repeatedly in an expression (the main example is a[i]=+
+i;)
• Many uses of explicit type conversion (casts), especially of reinterpret_cast
A.1.2 Program start and termination
A C++ program must have a single global function called main(). The program starts by executing
main(). The return type of main() is int (void is not a conforming alternative). The value returned by
main() is the program’s return value to “the system.” Some systems ignore that value, but successful
termination is indicated by returning zero and failure by returning a nonzero value or by an uncaught
exception (but an uncaught exception is considered poor style).
The arguments to main() can be implementation defined, but every implementation must accept two
versions (though only one per program):
