C++

A pointer is a variable, that holds not the value itself, but the memory address, where the value is stored. The pointer has a type which determines, how many bytes the value does occupy at it's memory location.

There are two operators * and & involved, the both come in two distinct usages, which we try to tell apart below. Furthermore we discuss three special cases: pointers of type void, pointers to functions, pointers to pointers.

This is the most common use, it defines a pointer to a memory address which stores values of a specific type.

               int * pInt = new int(5);      // on heap
               int * pInt = new int[5];      // on heap
               int[] intArray = ... ;        // on stack (CHECK)

Solves a pointer into it's referring object type and the concrete object respectively. [Löst einen Pointer auf in den dahinterstehenden Objekttyp bzw. das konkrete Objekt.]

               int *p = new int(5);      // pointer as usual
               dowhat1(*pInt);           // dereference p from pointer to value

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               int a = 5;
               int p = &a;  // p now contains the address of a

With references, a caller can pass a parameter to be changed by a function. If one return value is not enough, but we want two or more, we can to pass a parameter as a reference or as a pointer.

               ///void dowhat1(const int &a);
               ///void dowhat2(cont int *p);
               void dowhat1(int &a);            // declaration, note the &
               void dowhat2(int *p);            // declaration
               int a = 5;                       // declare plus initialaize a value
               dowhat1(a);                      // pass value, taken as reference
               dowhat2(&a);                     // pass the pointer

We neet them if we want deal with a pointer before we know it's final type.

               char* pChar = NULL;
               int* pInt = NULL;
               void* pVoid = NULL;
               getMem(pVoid);
               int t = getType(..);
               int s = getSize(..);
               int s2 = sizeof(..);
               if (t == 0)
                  pChar = (char*) pVoid;

It's a delegate mechanism ...

It's a typedef on function pointers ... (very difficult syntax)

               // supplement sample code ...

[It's not soo difficult ... we just need a telling example ...]

               // supplement sample code ...

Demos

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Literature

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• Scott Meyers: Effektiv C++ programmieren - 50 Wege zur Verbesserung Ihrer Programme und Entwürfe; 3. Auflage; Deutsche Übersetzung von Michael Tamm; Verlag Addison-Wesley 1998; 290 Seiten; ISBN 3-8273-1305-8. Amerikanische Orginalausgabe: Effective C++ - 50 Specific Ways to Improve Your Programs and Designs; ISBN 0-201-92488-9; (C) Copyright 1997 by Addison-Wesley Publishing Company (# 20110718.1141) Note: Standardbuch für fortgeschrittene C++-Entwickler.
• Scott Meyers: Mehr Effektiv C++ programmieren - 35 neue Wege zur Verbesserung Ihrer Programme und Entwürfe; Deutsche Übersetzung von Markus Beringmeier; Verlag Addison-Wesley 1999; 323 Seiten; ISBN 3-8273-1275-2. Amerikanische Orginalausgabe: More Effective C++, 35 New Ways to improve Your Programs and Design; ISBN 0-201-63371-X; (C) Copyright 1997 by Addison-Wesley Publishing Company (# 20110718.1142) Note: Standardbuch für fortgeschrittene C++-Entwickler.
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