C Pocket Reference

The Type void

The type specifier void indicates that no value is available. It is used in three kinds of situations:

Expressions of type void

There are two uses for void expressions. First, functions that do not return a value are declared as void. For example:

void exit (int status);

Second, the cast construction (void)expression can be used to explicitly discard the value of an expression. For example:

(void)printf("An example.");

Prototypes of functions that have no parameters

For example:

int rand(void);

Pointers to void

The type void * (pronounced “pointer to void”) represents the address of an object, but not the object’s type. Such “typeless” pointers are mainly used in functions that can be called with pointers to different types as parameters. For example:

void *memcpy(void *dest, void *source, size_t count);