UNIT 3

1. What is an array?

An array is defined as the collection of similar type of data items stored at contiguous memory locations. Arrays are the derived data type in C programming language which can store the primitive type of data such as int, char, double, float, etc. It also has the capability to store the collection of derived data types, such as pointers, structure, etc. The array is the simplest data structure where each data element can be randomly accessed by using its index number.

C array is beneficial if you have to store similar elements. For example, if we want to store the marks of a student in 6 subjects, then we don't need to define different variables for the marks in the different subject. Instead of that, we can define an array which can store the marks in each subject at the contiguous memory locations.

By using the array, we can access the elements easily. Only a few lines of code are required to access the elements of the array.

Properties of Array

The array contains the following properties.

• Each element of an array is of same data type and carries the same size, i.e., int = 4 bytes.
• Elements of the array are stored at contiguous memory locations where the first element is stored at the smallest memory location.
• Elements of the array can be randomly accessed since we can calculate the address of each element of the array with the given base address and the size of the data element.

Advantage of C Array

1) Code Optimization: Less code to the access the data.

2) Ease of traversing: By using the for loop, we can retrieve the elements of an array easily.

3) Ease of sorting: To sort the elements of the array, we need a few lines of code only.

4) Random Access: We can access any element randomly using the array.

Disadvantage of C Array

1) Fixed Size: Whatever size, we define at the time of declaration of the array, we can't exceed the limit. So, it doesn't grow the size dynamically like LinkedList which we will learn later.

2.     Explain declaration of an array and initialization of an array with examples

We can declare an array in the c language in the following way.

1. Data_type array_name[array_size];  

Now, let us see the example to declare the array.

1. Int marks[5];  

Here, int is the data_type, marks are the array_name, and 5 is the array_size.

Initialization of C Array

The simplest way to initialize an array is by using the index of each element. We can initialize each element of the array by using the index. Consider the following example.

1. Marks[0]=80;//initialization of array  
2. Marks[1]=60;  
3. Marks[2]=70;  
4. Marks[3]=85;  
5. Marks[4]=75;  

C array example

1. #include<stdio.h>  
2. Int main(){      
3. Int i=0;    
4. Int marks[5];//declaration of array       
5. Marks[0]=80;//initialization of array    
6. Marks[1]=60;    
7. Marks[2]=70;    
8. Marks[3]=85;    
9. Marks[4]=75;    
10. //traversal of array    
11. For(i=0;i<5;i++){      
12. Printf("%d \n",marks[i]);    
13. }//end of for loop     
14. Return 0;  
15. }    

Output

80

60

70

85

75

C Array: Declaration with Initialization

We can initialize the c array at the time of declaration. Let's see the code.

1. Int marks[5]={20,30,40,50,60};  

In such case, there is no requirement to define the size. So it may also be written as the following code.

1. Int marks[]={20,30,40,50,60};  

Let's see the C program to declare and initialize the array in C.

1. #include<stdio.h>  
2. Int main(){      
3. Int i=0;    
4. Int marks[5]={20,30,40,50,60};//declaration and initialization of array    
5. //traversal of array    
6. For(i=0;i<5;i++){      
7. Printf("%d \n",marks[i]);    
8. }    
9. Return 0;  
10. }    

Output

20

30

40

50

60

3. Write a program of Sorting an array and Program to print the largest and second largest element of the array

In the following program, we are using bubble sort method to sort the array in ascending order.

1. #include<stdio.h>    
2. Void main ()    
3. {    
4.    Int i, j,temp;     
5.    Int a[10] = { 10, 9, 7, 101, 23, 44, 12, 78, 34, 23};     
6.    For(i = 0; i<10; i++)    
7.    {    
8.        For(j = i+1; j<10; j++)    
9.        {    
10.            If(a[j] > a[i])    
11.            {    
12.                Temp = a[i];    
13.                a[i] = a[j];    
14.                a[j] = temp;     
15.            }     
16.        }     
17.    }     
18.    Printf("Printing Sorted Element List ...\n");    
19.    For(i = 0; i<10; i++)    
20.    {    
21.        Printf("%d\n",a[i]);    
22.    }    
23. }     

Program to print the largest and second largest element of the array.

1. #include<stdio.h>  
2. Void main ()  
3. {  
4.    Int arr[100],i,n,largest,sec_largest;  
5.    Printf("Enter the size of the array?");  
6.    Scanf("%d",&n);  
7.    Printf("Enter the elements of the array?");  
8.    For(i = 0; i<n; i++)  
9.    {  
10.        Scanf("%d",&arr[i]);  
11.    }  
12.    Largest = arr[0];  
13.    Sec_largest = arr[1];  
14.    For(i=0;i<n;i++)  
15.    {  
16.        If(arr[i]>largest)  
17.        {  
18.            Sec_largest = largest;  
19.            Largest = arr[i];  
20.        }  
21.        Else if (arr[i]>sec_largest && arr[i]!=largest)  
22.        {  
23.            Sec_largest=arr[i];  
24.        }  
25.    }  
26.    Printf("largest = %d, second largest = %d",largest,sec_largest);  
27.      
28. }  

4.     Explain 2 dimensional array in detail with example

The two-dimensional array can be defined as an array of arrays. The 2D array is organized as matrices which can be represented as the collection of rows and columns. However, 2D arrays are created to implement a relational database lookalike data structure. It provides ease of holding the bulk of data at once which can be passed to any number of functions wherever required.

Declaration of two dimensional Array in C

The syntax to declare the 2D array is given below.

1. Data_type array_name[rows][columns];  

Consider the following example.

1. Int twodimen[4][3];  

Here, 4 is the number of rows, and 3 is the number of columns.

Initialization of 2D Array in C

In the 1D array, we don't need to specify the size of the array if the declaration and initialization are being done simultaneously. However, this will not work with 2D arrays. We will have to define at least the second dimension of the array. The two-dimensional array can be declared and defined in the following way.

1. Int arr[4][3]={{1,2,3},{2,3,4},{3,4,5},{4,5,6}};  

Two-dimensional array example in C

1. #include<stdio.h>  
2. Int main(){      
3. Int i=0,j=0;    
4. Int arr[4][3]={{1,2,3},{2,3,4},{3,4,5},{4,5,6}};     
5. //traversing 2D array    
6. For(i=0;i<4;i++){    
7. For(j=0;j<3;j++){    
8.   Printf("arr[%d] [%d] = %d \n",i,j,arr[i][j]);    
9. }//end of j    
10. }//end of i    
11. Return 0;  
12. }    

Output

Arr[0][0] = 1

Arr[0][1] = 2

Arr[0][2] = 3

Arr[1][0] = 2

Arr[1][1] = 3

Arr[1][2] = 4

Arr[2][0] = 3

Arr[2][1] = 4

Arr[2][2] = 5

Arr[3][0] = 4

Arr[3][1] = 5

Arr[3][2] = 6

C 2D array example: Storing elements in a matrix and printing it.

1. #include <stdio.h>    
2. Void main ()    
3. {    
4.    Int arr[3][3],i,j;     
5.    For (i=0;i<3;i++)    
6.    {    
7.        For (j=0;j<3;j++)    
8.        {    
9.            Printf("Enter a[%d][%d]: ",i,j);                
10.            Scanf("%d",&arr[i][j]);    
11.        }    
12.    }    
13.    Printf("\n printing the elements ....\n");     
14.    For(i=0;i<3;i++)    
15.    {    
16.        Printf("\n");    
17.        For (j=0;j<3;j++)    
18.        {    
19.            Printf("%d\t",arr[i][j]);    
20.        }    
21.    }    
22. }    

Output

Enter a[0][0]: 56  

Enter a[0][1]: 10  

Enter a[0][2]: 30 

Enter a[1][0]: 34 

Enter a[1][1]: 21

Enter a[1][2]: 34   

Enter a[2][0]: 45

Enter a[2][1]: 56

Enter a[2][2]: 78  

Printing the elements ....

56      10      30 

34      21      34 

45      56      78

5.     Explain bubble sort with example

In Bubble sort, Each element of the array is compared with its adjacent element. The algorithm processes the list in passes. A list with n elements requires n-1 passes for sorting. Consider an array A of n elements whose elements are to be sorted by using Bubble sort. The algorithm processes like following.

1. In Pass 1, A[0] is compared with A[1], A[1] is compared with A[2], A[2] is compared with A[3] and so on. At the end of pass 1, the largest element of the list is placed at the highest index of the list.
2. In Pass 2, A[0] is compared with A[1], A[1] is compared with A[2] and so on. At the end of Pass 2 the second largest element of the list is placed at the second highest index of the list.
3. In pass n-1, A[0] is compared with A[1], A[1] is compared with A[2] and so on. At the end of this pass. The smallest element of the list is placed at the first index of the list.

Algorithm :

• Step 1: Repeat Step 2 For i = 0 to N-1
• Step 2: Repeat For J = i + 1 to N - I
• Step 3: IF A[J] > A[i]
  SWAP A[J] and A[i]
  [END OF INNER LOOP]
  [END OF OUTER LOOP
• Step 4: EXIT

Complexity

C Program

1. #include<stdio.h>  
2. Void main ()  
3. {  
4.    Int i, j,temp;   
5.    Int a[10] = { 10, 9, 7, 101, 23, 44, 12, 78, 34, 23};   
6.    For(i = 0; i<10; i++)  
7.    {  
8.        For(j = i+1; j<10; j++)  
9.        {  
10.            If(a[j] > a[i])  
11.            {  
12.                Temp = a[i];  
13.                a[i] = a[j];  
14.                a[j] = temp;   
15.            }   
16.        }   
17.    }   
18.    Printf("Printing Sorted Element List ...\n");  
19.    For(i = 0; i<10; i++)  
20.    {  
21.        Printf("%d\n",a[i]);  
22.    }  
23. }  

Output:

Printing Sorted Element List . . .

7

9

10

12

23

34

34

44

78

101

6.     Explain selection sort with example

In selection sort, the smallest value among the unsorted elements of the array is selected in every pass and inserted to its appropriate position into the array.

First, find the smallest element of the array and place it on the first position. Then, find the second smallest element of the array and place it on the second position. The process continues until we get the sorted array.

The array with n elements is sorted by using n-1 pass of selection sort algorithm.

• In 1st pass, smallest element of the array is to be found along with its index pos. Then, swap A[0] and A[pos]. Thus A[0] is sorted, we now have n -1 elements which are to be sorted.
• In 2nd pas, position pos of the smallest element present in the sub-array A[n-1] is found. Then, swap, A[1] and A[pos]. Thus A[0] and A[1] are sorted, we now left with n-2 unsorted elements.
• In n-1th pass, position pos of the smaller element between A[n-1] and A[n-2] is to be found. Then, swap, A[pos] and A[n-1].

Therefore, by following the above explained process, the elements A[0], A[1], A[2],...., A[n-1] are sorted.

Example

Consider the following array with 6 elements. Sort the elements of the array by using selection sort.

A = {10, 2, 3, 90, 43, 56}.

Sorted A = {2, 3, 10, 43, 56, 90}

Complexity

Algorithm

SELECTION SORT(ARR, N)

• Step 1: Repeat Steps 2 and 3 for K = 1 to N-1
• Step 2: CALL SMALLEST(ARR, K, N, POS)
• Step 3: SWAP A[K] with ARR[POS]
  [END OF LOOP]
• Step 4: EXIT

SMALLEST (ARR, K, N, POS)

• Step 1: [INITIALIZE] SET SMALL = ARR[K]
• Step 2: [INITIALIZE] SET POS = K
• Step 3: Repeat for J = K+1 to N -1
  IF SMALL > ARR[J]
  SET SMALL = ARR[J]
  SET POS = J
  [END OF IF]
  [END OF LOOP]
• Step 4: RETURN POS

C Program

1. #include<stdio.h>  
2. Int smallest(int[],int,int);  
3. Void main ()  
4. {  
5.    Int a[10] = {10, 9, 7, 101, 23, 44, 12, 78, 34, 23};  
6.    Int i,j,k,pos,temp;  
7.    For(i=0;i<10;i++)  
8.    {  
9.        Pos = smallest(a,10,i);  
10.        Temp = a[i];  
11.        a[i]=a[pos];  
12.        a[pos] = temp;  
13.    }  
14.    Printf("\nprinting sorted elements...\n");  
15.    For(i=0;i<10;i++)  
16.    {  
17.        Printf("%d\n",a[i]);  
18.    }  
19. }  
20. Int smallest(int a[], int n, int i)  
21. {  
22.    Int small,pos,j;  
23.    Small = a[i];  
24.    Pos = i;  
25.    For(j=i+1;j<10;j++)  
26.    {  
27.        If(a[j]<small)  
28.        {  
29.            Small = a[j];  
30.            Pos=j;  
31.        }  
32.    }  
33.    Return pos;  
34. }  

Output:

Printing sorted elements...

7

9

10

12

23

23

34

44

78

101

7.     What is function?

In c, we can divide a large program into the basic building blocks known as function. The function contains the set of programming statements enclosed by {}. A function can be called multiple times to provide reusability and modularity to the C program. In other words, we can say that the collection of functions creates a program. The function is also known as procedure or subroutine in other programming languages.

Advantage of functions in C

There are the following advantages of C functions.

• By using functions, we can avoid rewriting same logic/code again and again in a program.
• We can call C functions any number of times in a program and from any place in a program.
• We can track a large C program easily when it is divided into multiple functions.
• Reusability is the main achievement of C functions.
• However, Function calling is always a overhead in a C program.

Function Aspects

There are three aspects of a C function.

• Function declaration A function must be declared globally in a c program to tell the compiler about the function name, function parameters, and return type.

• Function call Function can be called from anywhere in the program. The parameter list must not differ in function calling and function declaration. We must pass the same number of functions as it is declared in the function declaration.

• Function definition It contains the actual statements which are to be executed. It is the most important aspect to which the control comes when the function is called. Here, we must notice that only one value can be returned from the function.

The syntax of creating function in c language is given below:

1. Return_type function_name(data_type parameter...){  
2. //code to be executed  
3. }  

8.     Give Example for Function without argument and return value

Example 1

1. #include<stdio.h>  
2. Void printName();  
3. Void main ()  
4. {  
5.    Printf("Hello ");  
6.    PrintName();  
7. }  
8. Void printName()  
9. {  
10.    Printf("Javatpoint");  
11. }  

Output

Hello Javatpoint

Example 2

1. #include<stdio.h>  
2. Void sum();  
3. Void main()  
4. {  
5.    Printf("\nGoing to calculate the sum of two numbers:");  
6.    Sum();  
7. }  
8. Void sum()  
9. {  
10.    Int a,b;   
11.    Printf("\nEnter two numbers");  
12.    Scanf("%d %d",&a,&b);   
13.    Printf("The sum is %d",a+b);  
14. }  

Output

Going to calculate the sum of two numbers:

Enter two numbers 10

24

The sum is 34

9.     What is C library function?

Library functions are the inbuilt function in C that are grouped and placed at a common place called the library. Such functions are used to perform some specific operations. For example, printf is a library function used to print on the console. The library functions are created by the designers of compilers. All C standard library functions are defined inside the different header files saved with the extension .h. We need to include these header files in our program to make use of the library functions defined in such header files. For example, To use the library functions such as printf/scanf we need to include stdio.h in our program which is a header file that contains all the library functions regarding standard input/output.

The list of mostly used header files is given in the following table.

10. Explain call by value and call by reference in detail with some examples

There are two methods to pass the data into the function in C language, i.e., call by value and call by reference.

Let's understand call by value and call by reference in c language one by one.

Call by value in C

• In call by value method, the value of the actual parameters is copied into the formal parameters. In other words, we can say that the value of the variable is used in the function call in the call by value method.
• In call by value method, we can not modify the value of the actual parameter by the formal parameter.
• In call by value, different memory is allocated for actual and formal parameters since the value of the actual parameter is copied into the formal parameter.
• The actual parameter is the argument which is used in the function call whereas formal parameter is the argument which is used in the function definition.

Let's try to understand the concept of call by value in c language by the example given below:

1. #include<stdio.h>  
2. Void change(int num) {    
3.    Printf("Before adding value inside function num=%d \n",num);    
4.    Num=num+100;    
5.    Printf("After adding value inside function num=%d \n", num);    
6. }    
7. Int main() {    
8.    Int x=100;    
9.    Printf("Before function call x=%d \n", x);    
10.    Change(x);//passing value in function    
11.    Printf("After function call x=%d \n", x);    
12. Return 0;  
13. }    

Output

Before function call x=100

Before adding value inside function num=100

After adding value inside function num=200

After function call x=100

Call by Value Example: Swapping the values of the two variables

1. #include <stdio.h>  
2. Void swap(int , int); //prototype of the function   
3. Int main()  
4. {  
5.    Int a = 10;  
6.    Int b = 20;   
7.    Printf("Before swapping the values in main a = %d, b = %d\n",a,b); // printing the value of a and b in main  
8.    Swap(a,b);  
9.    Printf("After swapping values in main a = %d, b = %d\n",a,b); // The value of actual parameters do not change by changing the formal parameters in call by value, a = 10, b = 20  
10. }  
11. Void swap (int a, int b)  
12. {  
13.    Int temp;   
14.    Temp = a;  
15.    a=b;  
16.    b=temp;  
17.    Printf("After swapping values in function a = %d, b = %d\n",a,b); // Formal parameters, a = 20, b = 10   
18. }  

Output

Before swapping the values in main a = 10, b = 20

After swapping values in function a = 20, b = 10

After swapping values in main a = 10, b = 20 

Call by reference in C

• In call by reference, the address of the variable is passed into the function call as the actual parameter.
• The value of the actual parameters can be modified by changing the formal parameters since the address of the actual parameters is passed.
• In call by reference, the memory allocation is similar for both formal parameters and actual parameters. All the operations in the function are performed on the value stored at the address of the actual parameters, and the modified value gets stored at the same address.

Consider the following example for the call by reference.

1. #include<stdio.h>  
2. Void change(int *num) {    
3.    Printf("Before adding value inside function num=%d \n",*num);    
4.    (*num) += 100;    
5.    Printf("After adding value inside function num=%d \n", *num);    
6. }      
7. Int main() {    
8.    Int x=100;    
9.    Printf("Before function call x=%d \n", x);    
10.    Change(&x);//passing reference in function    
11.    Printf("After function call x=%d \n", x);    
12. Return 0;  
13. }    

Output

Before function call x=100

Before adding value inside function num=100

After adding value inside function num=200

After function call x=200

Call by reference Example: Swapping the values of the two variables

1. #include <stdio.h>  
2. Void swap(int *, int *); //prototype of the function   
3. Int main()  
4. {  
5.    Int a = 10;  
6.    Int b = 20;   
7.    Printf("Before swapping the values in main a = %d, b = %d\n",a,b); // printing the value of a and b in main  
8.    Swap(&a,&b);  
9.    Printf("After swapping values in main a = %d, b = %d\n",a,b); // The values of actual parameters do change in call by reference, a = 10, b = 20  
10. }  
11. Void swap (int *a, int *b)  
12. {  
13.    Int temp;   
14.    Temp = *a;  
15.    *a=*b;  
16.    *b=temp;  
17.    Printf("After swapping values in function a = %d, b = %d\n",*a,*b); // Formal parameters, a = 20, b = 10   
18. }  

Output

Before swapping the values in main a = 10, b = 20

After swapping values in function a = 20, b = 10

After swapping values in main a = 20, b = 10