Why should we typedef a struct so often in C?

Question

I have seen many programs consisting of structures like the one below

typedef struct 
{
    int i;
    char k;
} elem;

elem user;

Why is i

Answer 1

One other good reason to always typedef enums and structs results from this problem:

enum EnumDef
{
  FIRST_ITEM,
  SECOND_ITEM
};

struct StructDef
{
  enum EnuumDef MyEnum;
  unsigned int MyVar;
} MyStruct;

Notice the typo in EnumDef in the struct (EnuumDef)? This compiles without error (or warning) and is (depending on the literal interpretation of the C Standard) correct. The problem is that I just created an new (empty) enumeration definition within my struct. I am not (as intended) using the previous definition EnumDef.

With a typdef similar kind of typos would have resulted in a compiler errors for using an unknown type:

typedef 
{
  FIRST_ITEM,
  SECOND_ITEM
} EnumDef;

typedef struct
{
  EnuumDef MyEnum; /* compiler error (unknown type) */
  unsigned int MyVar;
} StructDef;
StrructDef MyStruct; /* compiler error (unknown type) */

I would advocate ALWAYS typedef'ing structs and enumerations.

Not only to save some typing (no pun intended ;)), but because it is safer.