C-Tokens

C-Tokens:

the c-language program can contain the individual units called c-tokens.

• keywords
• Identifiers
• constants
• strings
• operators
• special symbols       

keywords:

• keywords also called as reserved words .
• keyword is a basic building block of c language.
• c-language has 32 keywords and each keyword has fixed meaning.
• keywords must be in lower case letters.

Identifiers:

• Identifiers are the names given to various program elements such as variables, functions,arrays,etc.

                      ex: int a;

Rules:

• 1st character can be alphabet or '_'
• Identifier cannot be a reserved word.
• it cannot support blank spaces.
• identifiers are case sensitive.
• they can be max of 32 characters any excess characters are ignore. 

Constants

• It is a fixed value that value cannot change during execution of the program.            

           In c-language we have memory constants and Symbolic constants

• memory constants:memory constants can be defined by using constkeyword.

             Syntax:     const  datatype  const-name = value;
             example:   const   float        pi               = 3.14;

• Symbolic constants: It can be defined by using preprocessor directive (# define).

              Syntax:     #define  symbolic-name   const-value
             example:    #define           PI              3.14               

String Declaration:

•  there is no String datatype in c language.
• so we have to use char array to declare a string.                                     

              char a[20];

• here array a can hold max of 19 characters and string leaves one location for \0.

variables:

• variable is a memory location name it store a value that value change during execution of program.

              example:
                              int a=10;
                              a=a+5;
                              a=a-6;

• value of a is finally  9.

declaration statement:

•  creating a variable and allocating the memory is known as declaration.

syntax:  datatype var-name1,var-name2...........;

                                  int   a,b,c;

Initializing variable:

• this can be done by using assignment operator(=),the variable can initialize while declaration itself. 

           example:        int a=30;
                                float b=30.33;

You can also refer

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•   C-Tokens
•   First C program
•   Functions
•   Structures