C Tokens For Beginners

 v C Tokens:-“It is a shortest unit of a program.”

(1)Keywords:- It is those words whose meaning has already been known to  the compiler. That is meaning to each keyword is fixed. All keyword  written in small case letters.

Examples:- auto, break, extern, char, const, double, else, enum, float, int , return, struct, void, union, while etc.

Types of Tokens:-

(2)Identifiers: Rules for writing identifiers

Ø First letter must be an alphabet or underscore.

Ø From second character onwards any combination of digits, alphabets, or underscore is allowed.

Ø Only digits , alphabets , underscore are allowed. No other symbol is allowed.

Ø Keywords cannot be allowed as identifiers.

Ø For ANSI   C max. length of identifiers is32.

Examples:-

Valid Identifiers	Non Valid Identifiers
Order-no name -err -246 abc_xyz123	x_$ big value order-no Sname Abc + 123 int

 v C Constants:- It refers the fixed value that don’t change during the execution of a program. They are also known as literals.

Types of C constants:-

 v Numeric Constants:-

(1)Integer constants:- These are three types.

Ø Decimal Constants:-“Sequence of digits 0 to 9 without fractional port”.

Ø Octal Constants:-“They have sequence of number from 0 to 7 and first digit must be zero.”

Ø Hexadecimal Constants:-“They have sequence of 0 to 9 and A to F (represent 10 to 15).”

(2)Real Constants:- They are number with fractional part that is number    with decimal point.                                                                                                                         

 Examples:- 10.70, 0.78, 0.45F.

         

Types of Real constants:-

         (a)Float.

         (b)Double

 v Non-Numeric Constants:-

(1)Single Character Constants:-They are enclosed in single quotes. They          consist of single character or digit.

Examples:- ‘4’,  ‘A’, ’\n’

(2)String Constants:-They are sequences of characters, digits, or any symbol enclosed in double quotes.

Examples:- “hello” ,   “24twenty four” ,   “$^ABCE” ,   ”123.23”

Backslash Constant:- These are some backslash constants

\b -----For back space \f------ For form feed \n----- For newline \r----- For carriage return \”----- For double quotes \0----- For null

\’ -----For single quotes \?-----For question mark \a-----For alert \t------For horizontal tab \v-----For  vertical tab

 Ø Backslash constant are also known as White Space Characters.

 Ø The printf function is used for recognizes all White Space Characters.

Comments are treated as White Space Characters by C compilers.

Operators:- “An operator denotes an operation to be performed on some data that generates some value”.

For Example :- Plus operator (+) on 2 and 6 generates 8.Here  2 and 6 are operands.

C is very rich in built-in operators. There are four types of operators.

(a) Arithmetic.

(b) Relational.

(c) Logical.

(d) Bitwise.

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