Array In C Program: - Easy To Learn

Introduction To Arrays:
In C programming, one of the frequently problem is to handle similar types of data. For example: if the user wants to store marks of 500 students, this can be done by creating 500 variables individually but, this is rather tedious and impracticable. These types of problem can be handled in C programming using arrays.

An array in C Programing can be defined as number of memory locations, each of which can store the same data type and which can be references through the same variable name. It is a collective name given to a group of similar quantities. These similar quantities could be marks of 500 students, number of chairs in university, salaries of 300 employees or ages of 250 students. Thus we can say array is a sequence of data item of homogeneous values (same type). These values could be all integers, floats or characters etc.
We have two types of arrays:

One-dimensional arrays.
Multidimensional arrays.
One Dimensional Arrays:
A one-dimensional array is a structured collection of components (often called array elements) that can be accessed individually by specifying the position of a component with a single index value. Arrays must be declared before they can be used in the program. Here is the declaration syntax of one dimensional
array:
data_type array_name[array_size];
Here “data_type” is the type of the array we want to define, “array_name” is the name given to the array and “array_size” is the size of the array that we want to assign to the array. The array size is always mentioned inside the “[]”.
For example:
Int age[5];

Initializing Arrays
Initializing of array is very simple in c programming. The initializing values are enclosed within the curly braces in the declaration and placed following an equal sign after the array name. Here is an example which declares and initializes an array of five elements of type int. Array can also be initialized after declaration. Look at the following code, which demonstrate the declaration and initialization of an array.
int age[5]={2,3,4,5,6};

It is not necessary to define the size of arrays during initialization e.g.
int age[]={2,3,4,5,6};
In this case, the compiler determines the size of array by calculating the number of elements of an array.

Accessing array elements
In C programming, arrays can be accessed and treated like variables in C.
For example:
 scanf(“%d”,&age[2]);
//statement to insert value in the third element of array age[]

 printf(“%d”,age[2]);
//statement to print third element of an array.
Arrays can be accessed and updated using its index.An array of n elements, has indices ranging from 0 to n-1. An element can be updated simply by assigning
A[i] = x;
A great care must be taken in dealing with arrays. Unlike in Java, where array index out of bounds exception is thrown when indices go out of the 0..n-1 range, C arrays may not display any warnings if outmof bounds indices are accessed. Instead,compiler may access the elements out of bounds, thus leading
to critical run time errors.

Example of array in C programming

/* C program to find the sum marks of n students using arrays */
#include <stdio.h>
int main()
{
  int i,n;
  int marks[n];
  int sum=0;
  printf("Enter number of students: ");
  scanf("%d",&n);
  for(i=0;i<n;i++)
  {
    printf("Enter marks of student%d: ",i+1);
    scanf("%d",&marks[i]); //saving the marks in array
    sum+=marks[i];
  }
  printf("Sum of marks = %d",sum);
return 0;
}

Output

Enter number of students: (input by user)3
Enter marks of student1: (input by user) 10
Enter marks of student2: (input by user) 29
Enter marks of student3: (input by user) 11
Sum of marks = 50

Important thing to remember in C arrays
Suppose, you declared the array of 10 students. For example: students[10]. You can use array members from student[0] to student[9]. But, what if you want to use element student[10], student[100] etc. In this case the compiler may not show error using these elements but, may cause fatal error during program execution.
Enter number of students: (input by user)3
Enter marks of student1: (input by user) 10
Enter marks of student2: (input by user) 29
Enter marks of student3: (input by user) 11
Sum of marks = 50

Multidimensional Arrays:
C programming language allows the user to create arrays of arrays known as multidimensional arrays.
To access a particular element from the array we have to use two subscripts one for row number and other for column number. The notation is of the form array [i] [j] where i stands for row subscripts and j stands for column subscripts. The array holds ij elements. Suppose there is a multidimensional array array[i][j][k][m]. Then this array can hold ijkm numbers of data. In the same way, the array of any
dimension can be initialized in C programming.

For example :
int smarks[3][4];

Here, smarks is an array of two dimension, which is an example of multidimensional array.

Make sure that you remember to put each subscript in its own, correct pair of brackets.
int a2[5, 7]; /* WRONG / a2[i, j] = 0; / WRONG / a2[j][i] = 0; / WRONG */
would do anything remotely like what you wanted

Initialization of Multidimensional Arrays

In C, multidimensional arrays can be initialized in different number of ways
int smarks[2][3]={{1,2,3}, {-1,-2,-3}};
OR
int smarks[][3]={{1,2,3}, {-1,-2,-3}};
OR
int smarks[2][3]={1,2,3,-1,-2,-3};

Coding example of Multidimensional Array:
This program asks user to enter the size of the matrix (rows and column) then, it asks the user to enter the elements of two matrices and finally it adds two matrix and displays the result.

Source Code to Add Two Matrix in C programming

#include <stdio.h>
int main()
{
  int r,c;
  int a[r][c];
  int b[r][c];
  int sum[r][c;
  printf("Enter number of rows (between 1 and 100): ");
  scanf("%d",&r);
  printf("Enter number of columns (between 1 and 100): ");
  scanf("%d",&c);
  printf("\nEnter elements of 1st matrix:\n");
/* Storing elements of first matrix entered by user.*/
  for(int i=0;i<r;++i)
  {
    for(int j=0;j<c;++j)
    {
      printf("Enter element a%d%d: ",i+1,j+1);
      scanf("%d",&a[i][j]);
    }
  }
/* Storing elements of second matrix entered by user. */
  printf("Enter elements of 2nd matrix:\n");
  for(int i=0;i<r;++i)
  {
    for(int j=0;j<c;++j)
    {
      printf("Enter element a%d%d: ",i+1,j+1);
      scanf("%d",&b[i][j]);
    }
  }
/*Adding Two matrices */
  for(int i=0;i<r;++i)
    for(int j=0;j<c;++j)
      sum[i][j]=a[i][j]+b[i][j];
/* Displaying the resultant sum matrix. */
  printf("\nSum of two matrix is: \n\n");
  for(int i=0;i<r;++i)
  {
    for(int j=0;j<c;++j)
    {
    printf("%d ",sum[i][j]);
      if(j==c-1)
      printf("\n\n");
    }
  }
return 0;
}

Output

Enter number of rows (between 1 and 100): 3
Enter number of rows (between 1 and 100): 2
Enter elements of 1st matrix:
Enter element a11: 4
Enter element a12: -4
Enter element a21: 8
Enter element a22: 5
Enter element a31: 1
Enter element a32: 0
Enter elements of 2nd matrix:
Enter element a11: 4
Enter element a12: -7
Enter element a21: 9
Enter element a22: 1
Enter element a31: 4
Enter element a32: 5
Sum of two matrix is:
8 -11
17 6
5 5

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