1.3 IDENTIFIER AND KEYWORDS

Identifiers are names given to various program elements,such as variables,functions and arrays.Identifiers consist of letters and digits,in any order,except that the first character must be a letter.Both uppercase and lowercase letters are permitted.The underscore character(_) can also be included.An identifier may also begin with an underscore,though tjis is rarely done in practice.

The following names are valid identifiers

x y12 sum_1 _temp TABLE


There are certain reserved words,called keywords,that have standard,predefined meanings in C.
These keywords can be used only for their intended purpose;they cannot be used as programmer defined identifiers.

These standard keywords are

auto extern sizeof break float static case for struct char goto

switch const if typedef continue int union default long unsigned

do register void double return volatile else short while enum signed

Note that the keywords are all lowercase.