As we saw in a simple program of C in the previous chapter, there are various words, letters and digits. Every word used in a C program is classified either as a Keyword or an Identifier. So in this tutorial you will learn about c programming keywords and identifiers.
C Programming Keywords
All the words used in C program which have fixed predefined meaning and whose meanings can’t be changed by the users are termed as Keywords. There are fixed number of keywords in C programming language and every keyword serves as a building block for program statements.
List of Keywords of ANSI C
|Note: Since C is a case sensitive programming language all the keywords must be written in lowercase.|
C Programming Identifiers
In the real world, when a new baby is born a name is given. Similarly, in C program when a new variable, function or an array is declared a particular name is given to them which is called an identifier. For example
apple is an identifier of integer type variable.
So identifiers are the user defined names. However, there are certain rules that must be followed while writing an identifier.
Rules for writing an identifier
- First letter of an identifier must be alphabet (underscore is also allowed)
- Identifier can only contain letters, digits and underscores
- Maximum length of identifier allowed is 31 characters
- White space is not allowed
- Keywords cannot be used as identifier