types and typecasts in c++


Every C++ Variable [1] needs a name and to know what kind of data [2] is stored as zero and ones in a portion of memory. We do not need to know where in memory the value is stored, because we can refer to the value by name, the identifier.

Primary Types

  • Integer int
  • Character char
  • Boolean bool true or false
  • Floating Point float
  • Double Floating Point double
  • Void void
  • Wide Character wchar_t

Note: Like in C, the width of integers are not fixed

One Solution is to use a type with a fixed width, for example: when you need a 64bit integer type, use int64_t or uint64_t.

The nullptr keyword is usable without including the header <cstddef>, unless you must use std::nullptr_t.

Derived Types

  • Function
  • Array
  • Pointer
  • References

User-defined Types

  • Class
  • Structure
  • Union
  • Enum
  • Typedef - typedef is to declare types

The identifier class in C++ is inspired by Simula (mathematicans). Structures are like Classes. Compared to Classes, they are identical, except Structs have public members and public inheritance by default.

typeid of <typeinfo> may return a mangled name, but can be used to debug.

  1. c++ variables
  2. types
  3. type
  4. integer


A Cast is to convert between types:

  • static_cast
  • reintepret
  • C-Style Cast
  • Remove const-cast
  • dynamic_cast

Static Cast


compile-time cast, no runtime check.

Remove const-cast

Casting away the constness of a read-only const variable. [1]

C-Style cast

For Example (int) or (int*)

Warning: Think before you use C-Style Casts, prefer a static_cast which is explicit and easier to find

In C++ the C-Style Cast is accepted by the Compiler as long as a const_cast, static_cast and reintepret_cast or a combination is applicable [2]. This can for example led to Compiler-Portability Issues.


polymorphic cast on Runtime. For Example for downcasts (from base to derived class) and crosscasts (accross the object hierarchy) of pointers to polymorphic objects.

Beyond the C++ Standard Library: Boost provides also polymorphic casts [3].

  1. const_cast
  2. explicit_cast
  3. boost: polymorphic_casts
Written on August 31, 2020
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