C – Character Set

After reading this character set topic, you will understand C Tokens, C Keywords and you will know the C Identifiers and Rule for defining identifiers.

Like any other programming language, C language has its own character set is used to form words, statements, and expression which makes programming easier.

C character set includes the following : –

lowercase letters        :-   a - z
uppercase letters        :-   A - Z
digits                   :-   0 - 9
Special characters       :-   ~ ' ! @ # % ^ & * () _ - + = | \ {} [] : ; <> , . ? /
white space characters   :-   blank space, horizontal tab, newline, form feed, vertical tab, 
                              carriage etc.

C – Tokens

In C program the smallest individual units known to compiler are known as tokens. C tokens are classified as shown below,

Keywords

Keywords are those words having fixed meaning in C language. In C list of all the keywords shown below:

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

Identifiers

Identifier are the name set to variables, data types, functions and labels. Identifier are the combination of alphabet letters i.e. uppercase (A to Z) and lowercase (a to z), digits (0 to 9), and the special character _ (underscore).

For example:

The statement in C is given by

int sum;

Indicate that

• int represent  integer data type.
• sum is identifier.

Rule for defining identifiers:

1.  An alphabet or underscore used in the starting letter of identifiers.

For example:

int _sum, sum_amount;

Here sum and sum_amount both are valid identifiers.

2. An identifier cannot be keywords or standard function name.

For example:

int else;

Here int else invalid identifier because else is keyword.

3. An identifier length up to 32 characters allowed.

4. Only underscore in special characters is allowed.

For example:

int sum_amount;

Here sum_amount is valid identifier.

5. Identifiers are case sensitive i.e. uppercase letters and lower case letters are different.

For example:

int sum,Sum;

Here, sum and Sum both are different identifiers.