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typedef

typedef type-declaration synonym ;

The typedef keyword defines a synonym for the specified type-declaration. The identifier in the type-declaration becomes another name for the type, instead of naming an instance of the type. You cannot use the typedef specifier inside a function definition.

A typedef declaration introduces a name that, within its scope, becomes a synonym for the type given by the decl-specifiers portion of the declaration. In contrast to the class, struct, union, and enum declarations, typedef declarations do not introduce new types — they introduce new names for existing types.

Example

//  Example of the typedef keyword
typedef unsigned  long   ulong ;

ulong  ul;      //  Equivalent to "unsigned long ul;"

typedef  struct  mystructtag
{
    int    i;
    float  f;
    char   c;
}  mystruct;

mystruct ms;    //  Equivalent to "struct mystructtag ms;"

typedef  int  ( * funcptr)();   //  funcptr is synonym for "pointer
                            //     to function returning int"

funcptr table[ 10 ];    //  Equivalent to "int (*table[10])();"