Keywords are the words whose meaning has already been explained to the C compiler (or in a broad sense to the computer). The keywords cannot be used as variable names because if we do so we are trying to assign a new meaning to the keyword, which is not allowed by the computer. Some C compilers allow you to construct variable names that exactly resemble the keywords. However, it would be safer not to mix up the variable names and the keywords. The keywords are also called ‘Reserved words’.
There are only 32 keywords available in C. Following Figure gives a list of these keywords for your ready reference.
Note that compiler vendors (like Microsoft, Borland, etc.) provide their own keywords apart from the ones mentioned above. These include extended keywords like near, far, asm, etc. Though it has been suggested by the ANSI committee that every such compiler specific keyword should be preceded by two underscores (as in __asm ), not every vendor follows this rule.