File in C

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Pointers in C

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Union in C

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Structure in C

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Functions in C

1.    Why User Defined Function is needed?

2.      Definition

3.      Function in C Language

4.      Return Values and their Types

5.      Arguments and Return value combination.

6.      Scope and lifetime of variables in functions

7.      Storage Classes

8.      Nesting of Functions

9.      Recursion

10.  Functions  and Arrays

11.  Summary

1.      Why User Defined Function is needed?
        ·         The large programs are divided into functional parts, then each part may be coded independently and then combined into a single unit.
       ·         Some type of operations are repeatedly used throughout the program. Such part can be written as a function and called whenever required .
       ·         It saves space and time also.
       ·         It reduces the length of the source program.
       ·         Top-down modular programming is done. i.e high level logic of the problem is solved first then details of lower level function solved.

2.      Definition
       Function is a set of statements which perform particular task together.

3.      Function in C Language
        C functions are divided into two categories

1.      Library function

Library functions are predefined. They are not needed to write by user.

e.g. scanf(),prinf,exit,

2.      User-defined function

These are defined by user at the time of writing program.

Syntax:

4.      Return Values and their Types

5.      Arguments and Return value combination.

6.      Scope and lifetime of variables in functions

Definitions:

Scope : It is a parts of program where variable is available for use.

Lifetime: It is a period during which variable retains a given value during execution of program.

Categories of variable:

1.      Local / Internal variable

A variables which are declared within particular function or block of the program.

2.      Global / external variable

    A variables which are declared outside of any function.

7.      Nesting of Functions

Nesting of function call is allowed in C Language.

e.g main function calls Function1(),Function1 calls Function2 and which in turns call another function such type of nesting is allowed

*Note: One cannot write function definition within another function definition 

                   Another example:

                                         function1(a, function2(p) );

8.      Recursion:

Definition:

 A Function which calls itself is known as recursion.

           e.g

int  Factorial(int n)

{

1.      if(n==1)

2.      return 1;

3.      else

4.      return(n*factorial(n-1));

}

Let us see detail execution of the recursion

In above function ,

n=5;

Now  value 1 is returned from factorial(1) function call is put into the previous function factorial(2) who calls factorial(1) and so on….

Let us see the sequence of execution .

Whole sequence of execution is as follows:
Red color -indicates statements are executed.
Blue color -indicates statements are in execution phase but not completed due to recursive call.
Black solid arrow-show the transfer of control because of recursive call.
Red dotted arrow-shows returning of control after recursive function call finishes.

9.      Functions  and Arrays

How to pass array to a function?

In Calling function: Pass an array name without subscript and size of an array

e.g            maximum(a,n);

                        Where a is an array name and n is the size of array.

In Function Definition:

Sample Program:

10.  Summary

·         Function is used to modularize the program.

·         Function can return only one value.

·         Function may or may not return a value.

·         Function return integer value by default.

·         Actual and formal parameter must be same in data type.

·         Function with return value must return some value with specified data type.

·         Function can have more than one return statements.

·         A Return statement can be written anywhere within function.

·         A function can be written before or after main function.

·         Function can not be defined inside another function.

·         A variable declared inside function is local to that function .It is destroyed when function is exited.

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Strings in C Language

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Arrays

Let us see an  Array  with following  points:

1. What is an Array?
2. Declaration of an Array.
3. Types of Array.
4. Initialization of an Arrays.
5. Solved Case Studies.

• What is an Array?

Array can be defined as follows:

1. It is a group of same type of elements.
2. It is a set of values of same data type.
3. Related data items share the common name .
4. Single name can be used to represent collection of same type of items.

E.g   Array of int ,Array of float ,Array of char etc.

• Declaration of an Array

Let us see how to declare Array in  C Language

Syntax:

      data_type Array_name[size_of_array];

This is one dimensional array where

         [] are used to specify Array_name is an array and inside bracket we mention the size of array means how many elements are hold by array_name

data_type Array_name[no_of_rows][no_of_column];

This is Two dimensional array

• Types of Array.

The type of an array depends on number of dimensions used.

The types are

1. 1-D array(One dimension Array)
2. 2-D Array(Two Dimension Array)
3. Multi Dimension array

• 1-D array(One dimension Array)

In this data is stored linearly in consecutive locations i.e it reserve consecutive memory locations for specified type of data with size_of_array.

e.g 

 int roll[10];

It declares an integer array roll with size 10.i.e Array with name roll can store 10 integer elements.

Each element is used with array name and it's subscript/index.

For array index always starts with 0 and ends with (size_of_array-1)

e.g

roll[0] -->This is the first element of an array

roll[1]

.

.

.

roll[9] -->This is the last element of an array.

Memory allocated for this array is calculated as follows:

Assume size of int is 2 bytes

Total consecutive Memory reserved/allocated is 2*10=20 bytes 

• 2-D Array(Two Dimension Array)

In this type data is stored in table format by using rows and columns

Syntax: 

1) int abc[10][5]; --> abc array has 10 rows and 5 columns

   i.e it can store 10*5=50 integer elements into array abc

2) char name[2][10]; -->name array has 2 rows and 10 columns

  i.e it can store 2*10=20 character elements into array name

Memory allocation for 2-D array.

Total memory for (rows*column) elements will be allocated.

In above 1st example ,

Assume size of int is 2 bytes

Total consecutive Memory reserved/allocated is 2*50=100 bytes

In above 2nd example ,

Assume size of char is 1 bytes .
Total consecutive Memory reserved/allocated is 1*20=20 bytes.

Each element in 2-D is used with array name and it's 2 subscript/index

e.g 

abc[0][0] -->this is the first element of an array 

abc[0][1]

..

abc[9][4] -->This is the last element of an array

• Multi Dimension array

Similar to 2D this uses multiple dimensions.

e.g

 int xyz[2][3][4];

• Initialization of an Arrays

Initialization means assigning initial values to elements in the array i.e at the time of declaration

1-D Array Initialization

   type arr-name[size]={comma separated list of values};

e.g 

int roll[10]={1,2,3,4,5,6,7,8,9,10};

   //it will initialize all 10 elements of roll array

int roll[10]={1,2,3,4};  

  //it will initialize only 1st 4 elements and remaining to zero(0)

Array Initialization without size

int roll[]={1,2,3,4,5,6}; 

  //It will declare roll array to contain 6 elements with initial vales as per given in list

char name[]={'R','I','Y','A'};

2-D Array Initialization

int roll[2][4]={1,1,1,1,2,2,2,2};

 //initialize row by row

 //first row to 1 and second row to 2

also written as

int roll[2][4]={{1,1,1,1},{2,2,2,2}};

if value missing in initialization then automatically set to zero.

e,

int roll[2][4]={{1,1},{2,2,2}};

//first 2 elements of 1st row to 1 and 1st 3 elements of 2nd row to 2 and remaining are set to zerog

Decision Making and Looping

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