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In the C++ programming language, a reference is a simple reference datatype that is less powerful but safer than the pointer type inherited from C. The name C++ reference may cause confusion, as in computer science a reference is a general concept datatype, with pointers and C++ references being specific reference datatype implementations.
Many languages have explicit pointers or references. Reference types differ from these in that the entities they refer to are always accessed via references; for example, whereas in C++ it's possible to have either a std:: string and a std:: string *, where the former is a mutable string and the latter is an explicit pointer to a mutable string (unless it's a null pointer), in Java it is only ...
The std::string type is the main string datatype in standard C++ since 1998, but it was not always part of C++. From C, C++ inherited the convention of using null-terminated strings that are handled by a pointer to their first element, and a library of functions that manipulate such strings.
A basic example is in the argv argument to the main function in C (and C++), which is given in the prototype as char **argv—this is because the variable argv itself is a pointer to an array of strings (an array of arrays), so *argv is a pointer to the 0th string (by convention the name of the program), and **argv is the 0th character of the ...
This was recognized as a defect in the standard and fixed in C++.) [4] C++11 and C11 add two types with explicit widths char16_t and char32_t. [5] Variable-width encodings can be used in both byte strings and wide strings. String length and offsets are measured in bytes or wchar_t, not in "characters", which can be confusing to beginning ...
Both the C99 and C++11 standards require at least one argument, but since C++20 this limitation has been lifted through the __VA_OPT__ functional macro. The __VA_OPT__ macro is replaced by its argument when arguments are present, and omitted otherwise. Common compilers also permit passing zero arguments before this addition, however. [4] [6]
A reference is an abstract data type and may be implemented in many ways. Typically, a reference refers to data stored in memory on a given system, and its internal value is the memory address of the data, i.e. a reference is implemented as a pointer. For this reason a reference is often said to "point to" the data.
The specification for pass-by-reference or pass-by-value would be made in the function declaration and/or definition. Parameters appear in procedure definitions; arguments appear in procedure calls. In the function definition f(x) = x*x the variable x is a parameter; in the function call f(2) the value 2 is the argument of the function. Loosely ...