In C programming language a predefined set of reserved words which provide computed control of various functions and declares in C compiler pre-processing libraries which perform special functions. The basic instructions are built up using a reserved set of words, for example main, for, if, else, switch, while, default, double, extern, for, and int, etc., Programming language C demands that they are used only for giving commands or making statements. Programmer cannot use default, for example, as the name of a variable. An attempt to do so will result in a compilation error.
In formal keywords are standard forms of identifiers that have standard predefined meaning in C compiler. Keywords are all lowercase, since uppercase and lowercase characters are not equivalent because C programming supports Case sensitivity, So it’s possible to utilize an uppercase keyword as an identifier but it’s not a good programming practice.
Note:
- Keywords are the words whose meaning has already been explained to the C compiler and their meanings cannot be changed. Hence keywords are also called ‘Reserved words’.
- Keywords can be used only for their intended purpose.
- Keywords serve as basic building blocks for program statements.
- Keywords can’t be used as programmer defined identifier.
- The keywords can’t be used as names for variables.
- All keywords must be written in lowercase.
- 32 keywords available in C.