These are the program elements such as variable name, function name, enumerator name, structure name, union name, etc..

Naming convention of Identifier:-

1. It always begins with any alphabet or underscore.
2. It is any combination of alphabet, digit & underscore.
3. Variable length is depend on the compiler.
4. No special symbol & no space are allowed except underscore.

These all are reversed word whose medium are predefined or precompiled means it has the special meaning & use to form a skeleton of the program.

The programmer can’t inter-fear in these words in the same way as you, in, an.

Keyword always written in the small letter.

There are 34 keywords in C which are as follows:-

1. void
2. char
3. int
4. short
5. long
6. float
7. double
8. signed
9. unsigned
10. for
11. while
12. do
13. if
14. else
15. switch
16. case
17. default
18. auto
19. static
20. extern
21. register
22. enum
23. struct
24. union
25. sizeof
26. const
27. volatile
28. break
29. continue
30. goto
31. return
32. near
33. far
34. huge

From 1 to 9 are used as a string data type(primary data type)

From 10 to 12 are used for loop control structure

From 13 to 14 are used for selection control statement

From 15 to 17 are used for case control structure

From 18 to 21 are used for storage class

From 22 to 24 are user defined data type

From 25 to 32 are miscellaneous

From 33 to 34 are pointers (additional keyword)

Small indivisual units of a program is called Tokens.

There are 6 types of Tokens in C which are as follows:-

1. Keyword
2. Identifier
3. Constants/Literals
4. Variable
5. Operator
6. Punctuator

C language is

• developed by:- Dennis M. Ritche
• developed at:- AT & T(American Telegraph & Telecommunication) Bell Lab, Marci Hill, New Jersey, USA
• developed on:- UNIX DEC PDP 11 Operating System
• developed in:- late 1972
• also called Structured Programming Language.

Why C language name is C?

In 1970 B language is developed by Ken Thomson. For making the continuation(B, C, …) its name is C (nothing more).