Programming in C

 Programming in C:

C is a middle level structure and procedural programming language is developed at "Bell Laboratory" (AT and T) in the year 1972 by "DENNIS RITCHIE".

Turbo 'C' was developed by borland international in the year 1989.

'C' character set :

1. Alphabets (both in upper and lower case). 
2. Digits (0 - 9) 
3. Special symbols ( !, #, &, $, +, -, =, <, >, {}, [], @, ;, etc) 

'C' data types:

1) primary data types - (character, integer, floating point, long integer, double, void) 

2) secondary data types - (array, pointer, etc) 

3) user-defined data types - (structure, union, enum etc). 

'C' data types, 'C' prefix and conversion specification:

Data type	‘C’ prefix	Conversion specification
character	char	%c
integer	int	%d
floating point	float	%f
long integer	long	%ld
double	double	%lf
void	void	0

Example of a program:

/* write a 'C' program to enter any two numbers and find out their sum and average */

# include < stdio.h>

# include < conio.h>

void main ()

{

     float a, b, sum, average ;

     clrscr () ;

     printf ( " enter any two number =  " ) ;

     scanf ( " %f%f%f ", and a, & b ) ;

     sum = a + b ;

     average = a + b/2 ;

     printf ( " \n sum = %f ", sum ) ;

     printf ( " \n average = %f ", average ) ;

     getch () ;

}

output:

enter any two number = 

     a = 5

     b = 7

sum = 5 + 7 = 12

average = 5 + 7/2 = 6

C Tokens and its Types:

 Each and every smallest individual unit in a C program are known as C tokens. 

C tokens are the basic building blocks in a C language which are constructed together to write a C program. 

Types-

C tokens are 6 types -

1. Identifier
2. Constant
3. String
4. Special symbols
5. Keywords
6. Operators

1. Identifier -

      Each C program elements are given a name called identifier. 

     Names are given to identify variable, functions, array etc. 

Rules for constructing identifier:-

• First character must be an alphabet. 
• Identifiers shouldn't be keywords. 
• Punctuation on a special character are not allowed except underscore. 
• Most identifiers are in lower case letter. 

2. Constant -

      Any value reference to constant. 

Variable :-

     Variable is the name given to computer memory cell where we can store constant. 

3.  String :-

       Collection of character enclose with a pair of ("  ") ( double quate) is known as string. 

4. Special symbols :-

     ( +,  -,  =, < , >, @, !,  #,  ;  , $, [], ) are special symbols. 

Escape sequence character :-

 These are non printing characters use for special operations inside a program. 

 \o = lulu

\n = new line

\" = double quate

\' = single quate

\b = back space

\t = horizontal tab

\v = vertical tab 

\\ =  back slash

5. Keywords :-

   Keywords are print find words in C compiler. These words have fix meaning and cannot be changed. 

   C language supports 32 keywords which are given below :-

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

6. Operators :-

        Operators are the special symbols use for the specific operation inside the expression. 

   Expression :-

       Constant, variable and function reference are joined together by various operators to form expression. 

Example -

   C=X + 3 ;

      ( here '+' is operator) 

Types of operators :-

      Operators are 6 types -

• arithmetical operator  -  ( + , - , / , % ,) 
• assignment operator -  (= , += , -= , \=) 
• relation operator - (< , > , <= , >= , ==) 
• logical operator - (&& (and) , ||(or) , >! (not) ) 
• increment &decrement operator- (++, --)
• conditional or ternary operator - (?, :) 
• size of operator- (  ) 
• bitwise operator - ( << , >> , & , ^) 

Statement use in 'C' language:

The statement are real building blocks of a C program. We can impliment our logic through different type of statement. 

Basically statement is two types :

1. Non executable statement
2. Executable statement.

1. Non executable statement :                             Non executable statement are not      compiled with C compiler. This is for program reference. 
2. Executable statement :                                   Executable statement are compiled         with C compiler. 

Executable statement basically 5 types :

• Declaration statement :  use to the declaration of variables, functions, modules to be use in program. 
• Input / output statement :  use to get input and give output to the program. 
• Conditional statement :  use to execution of program based on condition. 
• Iteration statement :  continue execution of statement. 
• Operational statement :  use to the execution of different operations through variable and operators. 

print f ( ) : To print the constant or contents                             of variable. 

scan f ( ) : To take input. 

clrscr ( ) : To clear the output print. 

getch ( ) :  To press the key from keyboard                          and display the output. 

As we know C is a middle level and procedural programming language. In this language we can solve and write a lot of programming problems. But when we come to write a C program we have to obey some rules. We can fulfill C program by obeying rules. Now we discuss the rules below. 

Rules to write a C program :

1. A 'C' program is a collection of functions or modules.

 
2. Each C program should be at least one function i.e main function / main ( ). 

3. Statements are written inside { }.

4. Each statement should be ended with (;). 

5. We need to include a required header file. 
     Syntax : 

        # include < header file name >

     Header file such as :

• # include < stdio. h >
• # include < conio. h >
• # include < math. h >
• # include < string. h >
• # include < graphics. h > etc

6. A comment line is a line i.e not compiled 

    with C compiler. This is given for user

    reference and used for documentation of

    program. 

    Note :

• A single line comment starts with //
• A multi line comment starts with /* and ends with */

    Example of a C program :                                 

    /* write a C program to print sum of 1 to 

    10 */

    # include < stdio. h >

    # include < conio. h >

     void main ( ) 

    {

      int sum = 0, n = 0 ;

      clrscr ( ) ;

      while ( n<=10) ;

      {

        sum = sum+10 ;

        n = n+1 ;

      }

      print f ( " the sum of 1 to 10 = %d", sum) ;

      getch ( ) ;

   }

 

Output :

 The sum of 1 to 10 = 55

7. Upper and lower case letters have the  

    rules where to be use in C language. 

8. Most statements, functions and modules   

    should be lower case letters. 

 Functions use in 'C' language:

Functions are predefined procedure and calculations which are already named for a easy use. 

Type of functions :

1. library function
2. user defined function 

1. Library function : These functions are present in 'C' library and these are predefined. 

Some library functions are us follow :   

•  print f ( ) 
•  scan f ( ) 
•  clrscr  ( ) 
•  getch  ( ) 
•  main  ( ) etc

2. user defined function : User can create their own functions for performing any specific task of the program. These type of function are called user defined function (UDF) . 

 To create and use these functions, we 

 should know these three things which are shown below. 

• function definition
• function declaration
• function calling

   Example : 

   

 /* write a C program to enter any two            numbers and find out their sum using UDF */ 

  # include < stdio. h >

  # include < conio. h >

  void main ( ) 

  {

     int a, b, c, s = 0;

     int sum ( int, int);

     clrscr ( );

     print f ( " enter any two numbers = " );

     scan f ( " %d %d ", & a, & b ) ;

     s = sum ( a, b );

     print f ( " sum of two numbers = %d ",s ); 

     getch ( ) ;

  }

  int sum ( int x, int y ) 

  {

    int p ;

       p = x + y ;

       return p ;

  }

Output:

Enter any two numbers =

                  8

                  2

Sum of two number = 10