1.4 Keywords

C defines several keywords, each with special meaning to the compiler. Keywords identify statement constructs and specify basic types and storage classes. Keywords cannot be used as identifiers and cannot be declared.

Table 1-3 lists the C keywords.

Table 1-3 Keywords

`auto`	`double`	`int`	`struct`
`break`	`else`	`long`	`switch`
`case`	`enum`	`register`	`typedef`
`char`	`extern`	`return`	`union`
`const`	`float`	`short`	`unsigned`
`continue`	`for`	`signed`	`void`
`default`	`goto`	`sizeof`	`volatile`
`do`	`if`	`static`	`while`
`__int8` (Alpha)	`__int16` (Alpha)	`__int32` (Alpha)	`__int64` (Alpha)
`__unaligned` (Alpha)	`__restrict`

Keywords are used as follows:

To assign a storage class to a variable or function (auto , extern , register , static )
To construct or qualify a data type (char , const , double , enum , float , int , __int64 (Alpha) , long , __restrict , short , signed , struct , __unaligned (Alpha) , union , unsigned , void , volatile )
As part of a statement (break , case , continue , default , do , else , for , goto , if , return , switch , while )
To define a new named type (typedef )
To perform an operation (sizeof )

Use of a keyword as a superfluous macro name is not recommended, but is legal; for example, to change the default size of a basic data type:

#define int short

Here, the keyword int has been redefined as short , which causes all data objects declared with the int data type to be stored as short objects.

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