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The alignment of particular fields in the struct (with respect to word boundaries) is implementation-specific and may include padding. Modern compilers typically support the #pragma pack directive, which sets the size in bytes for alignment. [1] The C struct feature was derived from the same-named concept in ALGOL 68. [2]
Here, the construct : re(0), im(0) is the initializer list. Sometimes the term "initializer list" is also used to refer to the list of expressions in the array or struct initializer. C++11 provides for a more powerful concept of initializer lists, by means of a template, called std::initializer_list.
C++ also provides constructors to initialize an object, but they are often not as convenient as the initializer list. However, C++03 allows initializer-lists only on structs and classes that conform to the Plain Old Data (POD) definition; C++11 extends initializer-lists, so they can be used for all classes including standard containers like std ...
C++ enforces stricter typing rules (no implicit violations of the static type system [1]), and initialization requirements (compile-time enforcement that in-scope variables do not have initialization subverted) [7] than C, and so some valid C code is invalid in C++. A rationale for these is provided in Annex C.1 of the ISO C++ standard.
Like fields marked as const they cannot change once initialized. The difference is that one can choose to initialize them in a constructor, or to a value that is not known until run-time. [12] This only works on fields. readonly fields can either be members of an instance or static class members.
C++ has enumeration types that are directly inherited from C's and work mostly like these, except that an enumeration is a real type in C++, giving added compile-time checking. Also (as with structs), the C++ enum keyword is combined with a typedef, so that instead of naming the type enum name, simply name it name.
The <inttypes.h> header (cinttypes in C++) provides features that enhance the functionality of the types defined in the <stdint.h> header. It defines macros for printf format string and scanf format string specifiers corresponding to the types defined in <stdint.h> and several functions for working with the intmax_t and uintmax_t types.
A snippet of C code which prints "Hello, World!". The syntax of the C programming language is the set of rules governing writing of software in C. It is designed to allow for programs that are extremely terse, have a close relationship with the resulting object code, and yet provide relatively high-level data abstraction.