C Programming, Constants and Variables..

In this tutorial you will learn about Character Set, C Character-Set Table, Special Characters, White Space, Keywords and Identifiers, Constants, Integer Constants, Decimal Integers, Octal Integers, Hexadecimal integer, Real Constants, Single Character Constants, String Constants, Backslash Character Constants [Escape Sequences] and Variables.

Instructions in C language are formed using syntax and keywords. It is necessary to strictly follow C language Syntax rules. Any instructions that mis-matches with C language Syntax generates an error while compiling the program. All programs must confirm to rules pre-defined in C Language. Keywords as special words which are exclusively used by C language, each keyword has its own meaning and relevance hence, Keywords should not be used either as Variable or Constant names.

Character Set

The character set in C Language can be grouped into the following categories.

1. Letters
2. Digits
3. Special Characters
4. White Spaces

White Spaces are ignored by the compiler until they are a part of string constant. White Space may be used to separate words, but are strictly prohibited while using between characters of keywords or identifiers.

C Character-Set Table



Upper Case A to Z

0 to 9

Lower Case a to z


Special Characters















.Minus Sign


.Question Mark


.Plus Sign



.Opening Angle (Less than sign)

.Quotation Marks


.Closing Angle (Greater than sign)


.Exclaimation Mark


.Left Parenthesis


.Vertical Bar


.Right Parenthesis




.Left Bracket




.Right Bracket




.Left Brace



.Right Bracket


.Dollar Sign


.Number Sign


.Percentage Sign

White Space

1. Blank Space
2. Horizontal Tab
3. Carriage Return
4. New Line
5. Form Feed

Keywords and Identifiers

Every word in C language is a keyword or an identifier. Keywords in C language cannot be used as a variable name. They are specifically used by the compiler for its own purpose and they serve as building blocks of a c program.

The following are the Keyword set of C language.





.size of





some compilers may have additional keywords listed in C manual.

Identifiers refers to the name of user-defined variables, array and functions. A variable should be essentially a sequence of letters and or digits and the variable name should begin with a character.

Both uppercase and lowercase letters are permitted. The underscore character is also permitted in identifiers.

3 Responses to C Programming, Constants and Variables..

  1. Darshan says:

    explain the use of in c programmin, xclusively in strings ????

  2. Darshan says:

    The use of !!

  3. nice one … thank you for sharing

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