4. Key words

There are certain reserved words, called keywords, which have standard, predefined meanings in C.

These keywords can be used only for their intended purpose; they cannot be used as programmer-defined identifiers.

Some standard keywords are:

auto extern sizeof break floatn static case for char

switch register return long int else while short void

Some C compilers may recognize other keywords.

Note that the keywords are all lowercase. Since uppercase and lowercase characters are not equivalent, it is possible to utilize an uppercase keyword as an identifier.

Normally, however, this is not done, as it is considered a poor programming practice.