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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 ...
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 ...
For example, C allows implicit conversion from void * to other pointer types but C++ does not (for type safety reasons). Also, C++ defines many new keywords, such as new and class, which may be used as identifiers (for example, variable names) in a C program.
Specifically, C allows a void* pointer to be assigned to any pointer type without a cast, while C++ does not; this idiom appears often in C code using malloc memory allocation, [9] or in the passing of context pointers to the POSIX pthreads API, and other frameworks involving callbacks. For example, the following is valid in C but not C++:
C appears to support assignment of array pointers, but in fact these are simply pointers to the array's first element, and again do not carry the array's size. [citation needed] In most languages, data types are not first-class objects, though in some object-oriented languages, classes are first-class objects and are instances of metaclasses.
C++ supports multiple inheritance of arbitrary classes. In Java a class can derive from only one class, [1] but a class can implement multiple interfaces [17] (in other words, it supports multiple inheritance of types, but only single inheritance of implementation). Java explicitly distinguishes between interfaces and classes.
Where "new" is the standard routine in Pascal for allocating memory for a pointer, and "hex" is presumably a routine to print the hexadecimal string describing the value of an integer. This would allow the display of the address of a pointer, something which is not normally permitted. (Pointers cannot be read or written, only assigned.)
In C++, classes can be forward-declared if you only need to use the pointer-to-that-class type (since all object pointers are the same size, and this is what the compiler cares about). This is especially useful inside class definitions, e.g. if a class contains a member that is a pointer (or a reference) to another class.