typedef

Typedef is a language feature in C and C++ that introduces an alias name for an existing type. It does not create a new type, but it provides another name for the same type, improving readability and portability.

Syntax: typedef existing_type new_name; Example: typedef unsigned long ulong; This allows you to use ulong in place of unsigned long. You can also typedef pointer types, arrays, and function pointer types, e.g., typedef int *IntPtr; typedef int (*CompareFn)(const void*, const void*).

Structs: In C, you often pair typedef with struct to avoid writing struct each time. Example: typedef struct Point { int x; int y; } Point; After this declaration, you can declare variables simply as Point p; without the struct keyword.

C++ considerations: In C++, typedef exists but the using alias declaration is preferred since C++11. For example, using Vec = std::vector<int>; is functionally equivalent to typedef std::vector<int> Vec; but the using form is often clearer, especially for templates.

Notes and limitations: Typedef creates an alias, not a distinct type or new type identity. It respects scope like any other declaration. It cannot introduce new template parameters or modify type behavior beyond providing an alternate name. When used with qualifiers like const or volatile, the qualifiers apply to the underlying type in the alias, which can affect how the alias interacts with pointers and references.