Typedef Aliases

The basic form

typedef unsigned long ulong;    // 'ulong' now names unsigned long
typedef int Score;              // Score is int, with intent

typedef does not create a new type — it creates a new NAME for an existing type. Score and int are interchangeable.

The classic: typedef struct

typedef struct {
    int x;
    int y;
} Point;                 // now 'Point', not 'struct Point'

Point p = {1, 2};        // no struct keyword needed

Or naming a tagged struct so it can self-reference:

typedef struct Node Node;
struct Node {
    int value;
    Node *next;          // self-reference needs the tag
};

You will build this Node in module 20.

When to alias

• burying unsigned long long behind u64
• typedef struct {...} Config; — the dominant C idiom
• naming semantic roles: typedef int UserId;