Introduction to C

 

 Introduction of C language  

C is a general-purpose programming language created by Dennis Ritchie at the Bell Laboratories in 1972.

It is a very popular language, despite being old. The main reason for its popularity is because it is a fundamental language in the field of computer science.

C is strongly associated with UNIX, as it was developed to write the UNIX operating system.

1.Header file:

1.Header file is a file that contains function deceleration and macro definition for c in built library.

2.All std. library function of c are in built in c.

3.we use it like #include<stdio.h>.

Examples:

• stdio.h: Contains functions for input and output.
• stdlib.h: Contains general-purpose functions like memory allocation, process control, etc.
• math.h: Contains mathematical functions.
• string.h: Contains functions for string manipulation.

2.Variables:  It collects memory for data or assign memory for data.                                               (Container for storing datatype)

Syntax  : data_type identifiers (var_name ).

Examples : int a; float a; char a; 

3.Types of Variables: There are two types of variables. 

 1. Local Variable.

 2. Global Variable.

A. Local Variables: 

1.These are declared within the function and cannot be accessed out side the function.

 2.The scope (range) of local variables will be within the function only.

  Program    :   

    #include<stdio.h> ------------------Header file

      int main ()

      {

               int a=10,b=20;  //a,b are local variable

               printf("a=%d, b=%d",a,b);

       }

Output :

B. Global Variables: 

1.This variables can be accessed any where from the program.

2. Tis variables are defined outside the main function.

3.Hence, this variable is visible to main function and all other sub function.

    Program    :  

      #include<stdio.h> ------------------Header file

        int a=10,b=20;  //a,b are Global variable

        int main ()

        {

                printf("a=%d, b=%d",a,b);

       }    

   Output     :

 4. Variables 

1.It is the name given to the variables.

2.Certain words like 'int' , 'main' etc. are some of the reserved key words and cannot be used as identifiers.

3. It contains alphabets , numbers or underscores and we cannot use double    underscores . Because they are case sensitive.

 Examples : total , sum , average , _m_, sum_1, sum1 .

 5.Keywords : 

     1.These words have their own meaning.

      2.These keywords are associated with there own specific  featrures.

     Examples : int , float , char , if , else, etc.

6.Data types : There are two types of datatypes .

1. Primary Data Type.

 2. Derived Data Type.

Primary Data Type	Derived Data Type
1.Integer	1.Array
2.Float	2.Pointer
3.Character	3.Structure
4.Double	4.Enumeration

 A. Primary data type :

Data type	Description	size	Examples
int  (%d)	Stores whole numbers, without decimals	2 or 4 bytes	1
float  (%f)	Stores fractional numbers, containing one or more decimals. Sufficient for storing 6-7 decimal digits.	4 bytes	1.99
double (%lf)	Stores fractional numbers, containing one or more decimals. Sufficient for storing 15 decimal digits.	8 bytes	1.99999
char (%c)	Stores a single character/letter/number, or ASCII values	1 byte	‘A’

B. Derived data  type :

  

Derived Data Type	Description
1.Array	It is collection similar data.
2.Pointers	It points to the address of another variable.
3.Structure	It is a collection of different type of data.

 The structure of a C program consists of the following sections:

 Header file

preprocessor; (semicolon means end of statement)

Global variable Declaretion

main ()

{

        Local Statement

        Block of Statement

}