Storing values in arrays

STORING VALUES IN ARRAYS

When we declare an array, we are just allocating space for its elements; no values are stored in 

the array. There are three ways to store values in an array. First, to initialize the array elements 

during declaration; second, to input values for individual elements from the keyboard; third, to 

assign values to individual elements. This is shown in below fig.

Figure: Storing values in an array

Initializing Arrays during Declaration

The elements of an array can be initialized at the time of declaration, just as any other variable. When an array is initialized, we need to provide a value for every element in the array. Arrays are initialized by writing,

type array_name[size]={list of values};

Note that the values are written within curly brackets and every value is 

separated by a comma. It is a compiler error to specify more values than there 

are elements in the array. When we write,

int marks[5]={90, 82, 78, 95, 88};

An array with the name marks is declared that has enough space to store five 

elements. The first element, that is, marks[0] is assigned value 90. Similarly, 

the second element of the array, that is marks[1], is assigned 82, and so on. 

This is shown in Fig below.

Fig : Initialization of array marks[5]

While initializing the array at the time of declaration, the programmer may omit the size of the array. For example,

int marks[]= {98, 97, 90};

The above statement is absolutely legal. Here, the compiler will allocate enough space for all the initialized elements. Note that if the number of values provided is less than the number of elements in the array, the un-assigned elements are filled with zeros. Figure below shows the 

initialization of arrays.

Fig : Initialization of array elements

Inputting Values from the Keyboard

An array can be initialized by inputting values from the keyboard. In this method, a while/do–while or a for loop is executed to input the value for each element of the array. For example, look at the code shown in Fig. Below

int i, marks[1 ];

for(i= ;i<1 ;i++)

scanf("%d", &marks[i]);

Figure: Code for inputting each element of the array

In the code, we start at the index i at 0 and input the value for the first element of the array. Since the array has 10 elements, we must input values for elements whose index varies from 0 to 9.

Assigning Values to Individual Elements

The third way is to assign values to individual elements of the array by using the assignment operator. Any value that evaluates to the data type as that of the array can be assigned to the individual array element. A simple assignment statement can be written as

marks[3] = 100;

Here, 100 is assigned to the fourth element of the array which is specified as marks[3].

Note that we cannot assign one array to another array, even if the two arrays have the same type and size. To copy an array, 

you must copy the value of every element of the first array into the elements of the second array. Figure below illustrates the code to copy an array.

 int i, arr1[1 ], arr2[1 ];

arr1[1 ]={ ,1,2,3,4,5,6,7,8,9};

for(i= ;i<1 ;i++)

arr2[i] = arr1[i];

Figure : Code to copy an array at the 

individual element level

The loop accesses each element of the first array and simultaneously assigns its value to the corresponding element of the second array. The index value i is incremented to access the next element in succession. Therefore, when this 

code is executed, arr2[0] = arr1[0], arr2[1] = arr1[1], arr2[2] = arr1[2], and so on.

We can also use a loop to assign a pattern of values to the array elements. For example, if we want to fill an array with 

even integers (starting from 0), then we will write the code as shown in below.

// Fill an array with even numbers

int i,arr[1 ];

for(i=0;i<10;i++)

arr[i] = i*2;

Figure: Code for filling an array with even numbers

In the code, we assign to each element a value equal to twice of its index, where the index starts from 0. So after executing this code, we will have arr[0]=0, arr[1]=2, arr[2]=4, and so on.