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C-TOKENS:


C-TOKENS:
            Each individual unit or element in a statement is called Token. C language contains different types of Tokens.

a. Identifiers
b. Variables
c. Data Types
d. Constants
e. Operators
f. Key Words
g. Delimiters

IDENTIFIERS:
In C-language names of variables, functions, labels and various other user-defined names or objects are called identifiers.

Rules for defining identifiers:

1. The first character must be an alphabet or an underscore, sub-sequent characters must be either letters, digits or underscore.
2. No space is allowed in between identifiers and no special characters are also allowed except underscore. 3. Key Words are not allowed as identifiers.
4. There is no limit of length of an identifier but some compilers will recognize only 8 or 32 characters.
Valid  Count1 , Test123 , Student_name Invalid  1count , 123test , Student-name

VARIABLES:
A variable is a data name that may be used to store a data value. A variable is a named location in memory that is used to hold a value that may be modified by the program. All variables must be declared before they can be used. The general syntax of declaration is

Syntax:  datatype variable list;
                Ex: int a,b,c;
                      float p,t,r;

VARIABLE INITIALIZATION:
            At the time of variable declaration we assign value to the variable is called variable initialization.

Ex:      int a;          variable declaration
           int a=10;    variable initialization

CONSTANTS:
Constant refers to fixed values that the program cannot alter. Constants can be any of the basic data types. Constants are also called “LITERALS”. There are 4 basic constants.They are
1. Integer Constants: Integer constants are specified as number without fractional components. Ex: 10, -20,
2. Floating Point Constants: Floating Point constants require the decimal point followed by the numbers fractional component. Ex: 11.23, -2.34 …
3. Character Constants: It is a single character enclosed in single quotes. Each character has an ASCII value to identify. Ex: ‘A’, ‘@’ , ….
 4. String Constants: A String is a set of characters enclosed in double quotes. Ex: “abc”, “c-language”, ….

 KEYWORDS:
Keywords are reserved words in C language. They have pre-defined meaning and are used for the intended purpose. Standard Keywords are


 auto                             const                                 int                          typedef 
break                            else                                  long                          switch 
case                              enum                               short                          union 
char                             extern                             register                      unsigned 
continue                       float                                signed                         void                                             default                         for                                  sizeof                         volatile  
do                                goto                                 static                          while 
double                         if                                       struct   

Comments

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