INTRODUCTION TO C PROGRAMMING

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INTRODUCTION TO C PROGRAMMING

                  
 C IS A GENERAL-PURPOSE, PROCEDURAL COMPUTER PROGRAMMING LANGUAGE THAT IS EXTREMELY POPULAR, SIMPLE AND FLEXIBLE. IT IS MACHINE-INDEPENDENT, STRUCTURED PROGRAMMING LANGUAGE.






ELEMENTS OF C LANGUAGE

CHARACTER SET
  •   LETTER  A TO Z  AND  a TO z 
  •   DIGITS 0 TO 9
  •   SPECIAL CHARACTERS :-  , . & - + ' " ! < > ? * ( ) : [ ] { } / \ $ % # ^ 
  •   WHITE SPACE :-  SPACE BAR, HORIZONTAL TAB, CARRIAGE RETURN, NEWLINE, FORM FEED.

C TOKENS 

  TOKEN IS THE SMALLEST INDIVIDUAL UNIT IN PROGRAM.







 
   
KEYWORDS
  
  ALL KEYWORDS HAVE A FIXED MEANING AND THIS MEANING CANNOT BE CHANGED.





EXAMPLE : INT - INTEGER VARIABLE TYPE




IDENTIFIERS

   IDENTIFIERS REFERS TO NAMES OF VARIABLE, FUNCTIONS, ARRAYS. THESE ARE USER DEFINED NAMES AND CONSIST OF LETTERS AND DIGITS, WITH LETTER HAS A FIRST CHARACTER.





RULES OF IDENTIFIERS

  •  THE FIRST CHARACTER MUST BE AN ALPHABET
  • MUST CONSIST OF ONLY LETTER, DIGITS, UNDERSCORE (_)
  • ONLY  31 CHARACTERS ARE SIGNIFICANT
  • CANNOT USE A KEYWORD
  • MUST NOT CONTAIN WHITE SPACE

CONSTANTS 

  CONSTANT REFERS TO FIXED VALUES THAT DO NOT CHANGE DURING THE EXECUTION OF A PROGRAM.



INTEGER CONSTANTS

   INTEGER CONSTANTS REFERS TO A SEQUENCE OF DIGITS.   





EXAMPLES :- 123, -321, 0, +78

REAL CONSTANTS

 THE QUANTITY THAT ARE REPRESENTED BY NUMBERS CONTAINING FRACTIONAL PARTS.





EXAMPLES :-  0.0083, -0.75, 435.36, +247.0

SINGLE CHARACTER CONSTANT

A SINGLE CHARACTER CONSTANT CONTAINS SINGLE CHARACTER ENCLOSED WITH IN A PAIR OF SINGLE QUOTES.





EXAMPLES :-  '5'  'X'  ';' 'B'

STRING CONSTANT

A STRING CONSTANT IS A SEQUENCE OF CHARACTER ENCLOSED IN DOUBLE QUOTES.





EXAMPLES :-  "HELLO"  "NAME"  "1987"


BACKSLASH CHARACTER CONSTANTS

IT IS  A SPECIAL CONSTANT THAT ARE USED IN OUTPUT FUNCTION.








VARIABLES

  A VARIABLE IS A DATA NAME THAT MAY BE USED TO STORE A DATA VALUE. A VARIABLE MAY TAKE DIFFERENT VALUES AT DIFFERENT TIMES DURING EXECUTION. IT IS A NAMED STORAGE REPRESENTATION.





DATA TYPE VARNAME1, VARNAME2,............., VARNAMEN;

DATA TYPES

A DATA TYPE IS A STORAGE REPRESENTATIONS AND MACHINE INSTRUCTION TO HANDLE CONSTANT VALUES.

C SUPPORTS 3 CLASS OF DATA TYPES

  1. PRIMARY DATA TYPES
  2. DERIVED DATA TYPES
  3. USER DEFINED DATA TYPES 
THERE ARE FIVE PRIMARY DATA TYPES NAMELY 
INTEGER (INT), CHARACTER (CHAR), FLOATING POINT (FLOAT), DOUBLE PRECISION FLOATING POINT (DOUBLE), VOID.




INTEGER DATA TYPE 

 INTEGERS ARE WHOLE NUMBERS WITH A RANGE OF VALUES SUPPORTED BY A PARTICULAR MACHINE.THE SIZE COMES IN 16 OR 32 BITS.THERE ARE 3 CLASSES OF INTEGERS.







CHARACTER DATA TYPE

 A SINGLE CHARACTER CAN BE DEFINED AS CHAR TYPE. IT IS STORED IN 8 BITS. THE QUALIFIER SIGNED OR UNSIGNED WHICH ALSO APPLICABLE TO THIS TYPE.






FLOATING POINT DATA TYPE

 FLOATING POINT NUMBERS ARE STORED IN 32 BITS WITH 6 DIGITS OF PRECISION.






DOUBLE DATA TYPE

DOUBLE DATA TYPE CAN BE USED FOR MORE PRECISION. DOUBLE DATA TYPE USES 64 BITS GIVING PRECISION 14 DIGITS  OF PRECISION.




TO EXTEND THE PRECISION FURTHER  WE CAN USE LONG DOUBLE.





VOID DATA TYPE

 THE VOID TYPE HAS NO VALUES. NORMALLY USED TO SPECIFY RETURN TYPE OF FUNCTIONS.






DECLARATION OF VARIABLES

 TO HANDLE DATA IN PROGRAMS WE SHOULD USE SUITABLE NAMES AND MUST BE DECLARED WITH APPROPRIATE DATA TYPES. DECLARATION GIVES TWO INFORMATION TO THE COMPILER.




  1.   WHAT IS THE VARIABLE NAME IS.
  2.   WHAT TYPE OF DATA THE VARIABLE WILL HOLD
EXAMPLE :-  INT C;

  TELLS THE COMPILER THE DATA TYPE IS INTEGER AND THE VARIABLE NAME IS C.


ASSIGNMENT OF VALUES TO VARIABLES

 A VALUE IS ASSIGNED TO A VARIABLE BY THE HELP OF EQUAL TO ( = ) OPERATOR. THE VALUE ON THE RIGHT HAND SIDE IS ASSIGN THE VARIABLE ON THE LEFT HAND SIDE. THE VALUE MAY BE DIRECT VALUE OR A STATEMENT.




  
EXAMPLE :-  C=10;   --------> DIRECT

                      SALARY = BP + TA + 0.15 * DA;

                       C = A;

                       C = A + B * C;

VALUES CAN  BE  ASSIGN TO THE VARIABLE AT A TIME OF DECLARATION.
EXAMPLE :-  INT  K = 1;
                      FLOAT   PI = 3.14;

MULTIPLE VARIABLE CAN BE DECLARE AND ASSIGN VALUES TO A SINGLE STATEMENT WITH THE HELP OF A COMMA ( , ) OPERATOR TO SEPARATE THE VARIABLE.

EXAMPLE  :-    INT   I  = 0, J = 1, K = 2;



STORAGE CLASSES

       A VARIABLE HAVE NOT ONLY DATA TYPE BUT ALSO STORAGE CLASS THAT PROVIDES INFORMATION ABOUT THEIR LOCATION AND VISIBILITY. A STORAGE CLASS DECIDES THE POSITION OF THE PROGRAM WITH IN WHICH THE VARIABLES ARE RECOGNIZED.

      C PROVIDES A VERITY OF STORAGE SPECIFIERS. THEY ARE AUTO, REGISTER, STATIC, EXTERN. BY DEFAULT THE VARIABLE AUTOMATIC (AUTO) STORAGE CLASS.
AN EXTERNAL TYPE  ( EXTERN ) ALSO KNOWN AS GLOBAL VARIABLE THAT MEANS A GLOBAL VARIABLE CAN BE ANY WHERE IN THE PROGRAM INCLUDING SUB-PROGRAM (FUNCTIONS). A VARIABLE DECLARED INSIDE A FUNCTION KNOWN AS LOCAL VARIABLE. WHICH IS LOCAL TO THAT PARTICULAR FUNCTION.

EXAMPLE  :-   

/* EXAMPLE OF STORAGE CLASS*/
                         
INT   M;  ----> GLOBAL VARIABLE

MAIN (  )

{
                           
INT   I;   ----> LOCAL VARIABLE

FLOAT BALANCE;

.........................
.........................
.........................

FUNCTION ( );

}



 

READING DATA FROM KEYBOARD

    ANOTHER WAY OF GIVING VALUES TO VARIABLES THROUGH INPUT DATA BY THE KEYBOARD, WE USE SCANF FUNCTION TO READ DATA FROM THE KEYBOARD. THE FORMAT OF SCANF FUNCTION IS AS FOLLOWS.




SCANF("CONTROL STRING",&VARIABLE1,&VARIABLE2 ......);

EXAMPLE  :-   SCANF("%D",&NAME);

   THE CONTROL STRING CONTAINS THE FORMAT OF DATA. THE AMPERSAND (&) BEFORE EACH VARIABLE NAMES SPECIFIES THE VARIABLE NAME'S ADDRESS. PRINTF PRINTING OUTPUT ON THE SCREEN. THE CONTROL STRING CONTROLS THE FORMAT OF OUTPUT. WE CAN USE THE BACKSLASH CONSTANTS TO FORMAT THE OUTPUT. FORMAT OF PRINTF.

PRINTF("CONTROL STRING",VARIABLE1,VARIABLE2,......);

EXAMPLE :-  PRINTF("SUM = %D",SUM);


SIMPLE C PROGRAM TO PRINT HELLO WORLD

 # include<stdio.h> 

 # include<conio.h>

 void main( )

{ 

printf("\nHELLO WORLD");

getch( );

} 


DEFINE SYMBOLIC CONSTANT

     CONSTANTS VALUES MAY APPEAR REPEATEDLY IN A NUMBER OF PLACE IN PROGRAM. IN THAT CASE TWO PROBLEMS.
  1. PROBLEM IN MODIFICATION OF PROGRAM
  2. PROBLEM IN UNDERSTANDING THE PROGRAM
SYMBOLIC NAMES ARE SOME TIMES CALLED CONSTANT IDENTIFIERS.  
                     
A CONSTANT  IS DEFINED AS FOLLOWS.

#  DEFINE  SYMBOLIC NAME     VALUE OF CONSTANT

EXAMPLE :-   #  DEFINE    PI    3.14


DECLARING  A VARIABLE AS CONSTANT

  WE CAN MAKE A CERTAIN VARIABLE VALUE TO REMAIN CONSTANT USING THE QUALIFIER  ' CONST '.

EXAMPLE :-   CONST INT   COUNT=10;

 





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