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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 ...
Further, because C and C++ expose pointers and references directly, there is a distinction between whether the pointer itself is constant, and whether the data pointed to by the pointer is constant. Applying const to a pointer itself, as in SomeClass * const ptr , means that the contents being referenced can be modified, but the reference ...
C++ Java Extends C with object-oriented programming and generic programming. C code can most properly be used. Strongly influenced by C++/C syntax. Compatible with C source code, except for a few corner cases. Provides the Java Native Interface and recently Java Native Access as a way to directly call C/C++ code.
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++:
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.
Array types in C are traditionally of a fixed, static size specified at compile time. The more recent C99 standard also allows a form of variable-length arrays. However, it is also possible to allocate a block of memory (of arbitrary size) at run-time, using the standard library's malloc function, and treat it as an array.
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.
Note: Java does not support pointers. [6] It is because pointers (with restrictions) are the default way of accessing objects in Java, and Java does not use stars to indicate them. For example, i in the last example is a pointer and can be used to access the instance. One can also declare a pointer to "read-only" data in C++.