types of constant

Now start c language

Character set :- It is a group of words, number and expression that is used to develop and run a program.

Syntax :-like any other language “c” also has its own vocabulary and grammer they are called syntax.

Identifier :- it refers to the name of variable, function and array it is complete user define names.

Constant :- A constant has fixed value that cannot change during the execution of program.

Variable  :- A variable is an entity that may be change during the  execution of program.

Keyward :- keyword are the word that carries special   meaning. All the keyword has fixed meaning it can’t be change. There are 32 keywords in c.

                                       

Constant in c

Types of constant 

Primary constant

i.                             Integer  (%d)

ii.                         Real     (%f)

iii.                     Character  (%c)

Secondary constant

i.                             Array

ii.                         Pointer

iii.                     String

iv.                      Enumerator

v.                          Structure

vi.                      Union

Rule for constructing integer constants

a.               A integer constant must have at least one number.

b.              It have no decimal point.

c.               It can be positive and negative.

d.              If no sign is there than, it assumed as positive. 

e.               No comma or blanks are allowed within integer constant .

                           example :- 425

                              +898

                                     -565

                                For print integer we use %d  in c language.

Rule for constructing real constants

Real constant are called floating point constant.

Real constant can we written in two form: -  1. Fractional form

                 2. Exponential form.

(i)                      A real constant have at least one digit .

(ii)                  It must have a decimal point .

(iii)              It can be positive or negative .

(iv)               If no sign is there than, it assumed as positive. 

(v)                   No comma or blanks are allowed within real constant .

Example :- 13.2

                        -27.8

                        +12.1

For print real constant we use %f .

The exponential form is use when value is too small and  large . The exponential  form are represent in two part . The part appearing before ‘e’ is called mantissa, whereas the part following  ‘e’ is called exponent .

Example :- 0.000342 can be written in  exponential form 3.42 x 10-4.

Rule for constructing character  constants

1.    a character constant is a single alphabet, a single digit or a single special symbol enclosed with single inverted commas.

2.   both the inverted commas should point to the left.

Example :- ‘a’

                    ‘=’

’+’

‘8’

For print a character we use %c.

Variable in c

Variable :- A variable is an entity that may be change during the  execution of program.

                                        Rules for constructing variable names.

a   a). A variable name is any combination of 1 to 31 alphabets,underscores.

b   b). The first character of variable should be alphabet or underscore.

     c).  No commas or blanks are allowed in variable name.

  Example:- int a,b ;

                        float c ;

                        char d;

A,b,c,d are the variables ant int ,float and char are data type.

keyward

Keyword :- keyword are the word that carries special   meaning. All the keyword has fixed meaning it can’t be change. 

There are 32 keywords in c. We cannot use keyword as word because we are assign new meaning to keyword, which is not allowed.

All the keywords written in small letter.

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