Data types :-

*      Data types refers to which types of value to be stored into the variable.
*      There are mainly two types of data types are available in c. language.

   1. Primary Data types / Built-in Data types
   2. User Defined Data types / Derived Data types

   1. Integer Datatype :-

*      We can use integer datatypes to store numeric values.
*      C. language supports integer datatypes in both signed and unsigned.
*      Integer datatpes has three types as short int, int and long int.

Types	Size (Bytes)	Range
short int or signed short int	1	-128 to 127
int or signed int	2	-32768 to 32767
long int or signed long int	4	-2,147,483,648 to 2,147,483,647
unsigned short int	1	0 to 255
unsigned int	2	0 to 65535
unsigned long int	4	0 to 4,294,967,295

   2. Floating point Datatype :-

*      Floating point datatypes can be used to store numeric values with decimal point.
*      There are threen floating types available in c. language.

Types	Size (Bytes)	Range
float	4	3.4e-38 to 3.4e+38
double	8	1.7e-308 to 1.7e+308
long double	10	3.4e-4932 to 3.4e+4332

   3. Charater Datatype :-

*      Character datatype can be used to store a single character value.

Types	Size (Bytes)	Range
char. or signed char.	1	-128 to 127
unsigned char.	1	0 to 255

   4. Void Datatype :-

*      The void datatype has no values. The type of function does not returned any value at that time we can use void type.

Datatype	Format specifier
int	%d
character	%c
float	%f
double	%ld
long double	%LD

Character Set :-

*    The character in c language that can be used in the c program. There are for types of character set available in c language.

Character Set	Symbol
Letters	Upper Case -> A to Z Lower Case -> a to z
Digit	, Comma . Dot ; Semicolon : Colon ? Question Mark ' Single Quote " Double Quote ! Exclamation | Pipe / Forward Slash or Slash \ Back Slash ~ Tiled _ Under Score $ Dollar % Percentage & Ampersand ^ Caret * Asterisk - Minus + Plus < Opening Angular Bracket > Closing Angular Bracket ( Left Parenthesis ) Right Parenthesis [ Left Square Bracket ] Right Square Bracket { Left Brace or Left Curly Bracket } Right Brace or Right Curly Bracket # Hash
White Space	Blank Space Horizontal Tab Carriage Return New Line Form Feed

Best Structure of "C" Program in c language

Structure of "C" Program

Document Section

Link Section

Definition Section

Global Declaration Section

Main() Section

{    Declaration Part }    Executable Part

Sub Program Section    Function 1() --    Function 2()    |    .................        |--> UDF    .................        |    Function n() --

(1) Documentation Section :-

*    The documentation section consist of a set of comment lines in the c program, comments, are the user defined message that are not compiled by compiler.
*    The example of comments the name of program , date, etc. *    There are type types of comments are available in c language.

Single line comment :-

*    We can specify a single line comment by using //symbol.
Ex :-      //This is single line comment

Multi line comment :-

*    We can specify a multi line comment by using /*.......*/.
Ex :-      /* This is multi line commnet
                 Developer Bhautik Jivani
                 Date :- 03-Jul-2018   */

(2) Link Section :-

*    This section provides the instructions to the compiler to link function from the system library.
*    This section includes the header files are stored in the c library. These header files contains the different library functions of c language.
*    The header files must be included in the c program.

Ex :-     #include<stdio.h> (Standard Input Output)
             #include<conio.h> (Console Input Output)

(3) Definition Section :-

*    This section contains all the symbolic constants. Constants means the fixed value for defining a contsant value. We can use # Define Statement.

e.g. :-     #define PI 3.14
*    Here variable PI has fixed value that is 3.14. That does not change during the execution of the program.

(4) Global Declaration Section :-

*    There are some user defined functions and variables are define globally that is in more than one function.
*    Such variables are known as global variables and they are declaredin the global declaration section.

(5) Main() Section :-

*    The c language must have one main function.
*    The main function is a special function used by c language to tell the computer where the program starts.
*    This section contains two parts:

Declaration Part :-

*    It declares the variables that can be used in the executable part.

Executable Part :-

*    It executes the statements. There is at least one executable statement. That main function starts with { & ends with }.

(6) Sub program/Function :-

*    This section contains all the user defined functions. That are called in the main function.

//This is first e.g. to print Bhautik

#include<stdio.h>
#include<conio.h>
void main()
{
    clrscr();
    printf("Bhautik");
    getch();
}