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In C/C++, it is possible to declare the parameter of a function or method as constant. This is a guarantee that this parameter cannot be inadvertently modified after its initialization by the caller. If the parameter is a pre-defined (built-in) type, it is called by value and cannot be modified. If it is a user-defined type, the variable is the ...
The C++ convention is instead to associate the * with the type, as in int* ptr, and read the const as modifying the type to the left. int const * ptrToConst can thus be read as "*ptrToConst is a int const" (the value is constant), or "ptrToConst is a int const *" (the pointer is a pointer to a constant integer). Thus:
immutable is a stronger variant of const, indicating data that can never change its value, while const indicates data that cannot be changed through this reference: it is a constant view on possibly mutable data. shared is used for shared data in multi-threading (as volatile was briefly used for in C++).
Information about the actual properties, such as size, of the basic arithmetic types, is provided via macro constants in two headers: <limits.h> header (climits header in C++) defines macros for integer types and <float.h> header (cfloat header in C++) defines macros for floating-point types. The actual values depend on the implementation.
In C and C++ short, long, and long long types are required to be at least 16, 32, and 64 bits wide, respectively, but can be more. The int type is required to be at least as wide as short and at most as wide as long , and is typically the width of the word size on the processor of the machine (i.e. on a 32-bit machine it is often 32 bits wide ...
In 1989, C++ 2.0 was released, followed by the updated second edition of The C++ Programming Language in 1991. [32] New features in 2.0 included multiple inheritance, abstract classes, static member functions, const member functions, and protected members. In 1990, The Annotated C++ Reference Manual was published. This work became the basis for ...
Due to its limitations, C and C++ language features have been added over the years to minimize the value and need for the preprocessor. Constant. For a long time, a preprocessor macro provided the preferred way to define a constant value. An alternative has always been to define a const variable, but that results in consuming runtime memory.
For example, even though most implementations of C and C++ on 32-bit systems define type int to be four octets, this size may change when code is ported to a different system, breaking the code. The exception to this is the data type char , which always has the size 1 in any standards-compliant C implementation.