How to use arrays in C / C++
In this tutorial, we will learn how to use array
in C / C++. This is one of the basic knowledge in C / C++ programming language, so please learn it carefully.
We will learn to declare, initialize, and access array
elements in C++ programming with the help of examples.
In the C and C++ programming languages, an array
is a variable that can store multiple values of the same data type.
For example: Suppose in a class there are 30 students. To store student information, instead of declaring 30 variables, we can use an array
with 30 elements.
So, how to declare an array
in C / C++? How to use it? Let's get started now !!!
What is an array in C / C++?
In the C and C++ programming languages, array
is a collection of similar data items stored at contiguous memory locations and elements can be accessed randomly using indices of an array
.
They can be used to store the collection of primitive data types such as int
, float
, double
, char
, etc of any particular type. In addition, arrays can also store derived data types such as structures
, pointers
, etc.
Why do we need arrays?
When we have a large number of variables of the same data type. Instead of using the usual way of storing by declaring variables, we can use an array
to store.
Let's take a look at some advantages and disadvantages of arrays
in C / C++:
Advantages:
- Retrieves random elements, based on the array's indices.
- The program looks cleaner, more optimized.
- Easily access array elements.
- Easy data manipulation.
- Easily sort data.
Disadvantages:
- The
array
has a fixed size.
Declare arrays in C / C++
To declare an array
, define the variable type, specify the name of the array
followed by [ ]
and specify the number of elements it should store.
dataType arrayName[arraySize];
Here,
- dataType: This is the data type of the
array
, which can be int, float,... . - arrayName: This is the name of the
array
, we will use it when calling thearray
. - arraySize: This is the size of the
array
. It determines how many elements anarray
can store.
For example: Suppose we want to declare an array
of integers number[] with 6 elements.
int number[6];
Initializing arrays in C / C++
When declaring an array
, we can initialize the value of the array
, for example as follows:
// declare and initialize and array int number[6] = {1, 2, 3, 5, 6, 7};
In the above code, the array
number[] has 6 elements and we initialize it with the values {1, 2, 3, 5, 6, 7} respectively.
Array
size is set in [ ]
and array
elements are set in { }
.Another method to initialize array
during declaration:
// declare and initialize and array int number[] = {1, 2, 3, 5, 6, 7};
In addition, we can initialize an element in the array
. Instead of initializing the elements of the array
.
int number[5]; number[0] = 1;
Adding elements to an array in C / C++
To add elements to the array
, we need to know the size of the array
.
Use a for loop to iterate from 0 to the size of the array
. For each iteration, we perform value initialization for an element. The result after the loop ends, we get an array
of elements.
For example: The program adds elements to the array
.
C++ programming:
#include <iostream> using namespace std; int main() { int n; do{ cout<<"Enter the size of the array: "; cin>>n; if(n <= 0) cout<<"Please enter the size of the array greater than 0 !!!\n"; }while(n <= 0); int arr[n]; for(int i = 0; i <= n - 1; i++){ cout<<"Enter the element "<<"[" <<i<<"]: "; cin>>arr[i]; } cout<<"\n-------------------------------\n"; cout<<"This program is posted at learnnc.com"; return 0; }
C programming:
#include <stdio.h> int main(void) { int n; do{ printf("Enter the size of the array: "); scanf("%d", &n); if(n <= 0) printf("Please enter the size of the array greater than 0 !!!\n"); }while(n <= 0); int arr[n]; for(int i = 0; i <= n - 1; i++){ printf("Enter the element [%d]: ",i); scanf("%d", &arr[i]); } printf("\n-------------------------------\n"); printf("This program is posted at learnnc.com"); return 0; }
Output:
Access the elements of an array in C / C++
In the C and C++ languages, the elements of an array
are associated with a number. That number is called the index of the element. We can access the element of the array
through it.
// syntax to access array elements array[index];
Example: Let's say we have an array
of numbers [] = {1, 2, 3, 4, 5, 6}. Now to get the 3rd element in the array
and then assign it to the variable N, we do the following.
int N = number[3]; // output N = 4
So how can I access all the elements in the array
? See the example below.
Example: Retrieve the elements in the array
.
C++ programming:
#include <iostream> using namespace std; int main() { int n; do{ cout<<"Enter the size of the array: "; cin>>n; if(n <= 0) cout<<"Please enter the size of the array greater than 0 !!!\n"; }while(n <= 0); int arr[n]; for(int i = 0; i <= n - 1; i++){ cout<<"Enter the element "<<"[" <<i<<"]: "; cin>>arr[i]; } cout<<"Elements in array is: "; for(int i = 0; i <= n - 1; i++){ cout<<arr[i]<<" "; } cout<<"\n-------------------------------\n"; cout<<"This program is posted at learnnc.com"; return 0; }
C programming:
#include <stdio.h> int main(void) { int n; do{ printf("Enter the size of the array: "); scanf("%d", &n); if(n <= 0) printf("Please enter the size of the array greater than 0 !!!\n"); }while(n <= 0); int arr[n]; for(int i = 0; i <= n - 1; i++){ printf("Enter the element [%d]: ",i); scanf("%d", &arr[i]); } printf("Elements in array is: "); for(int i = 0; i <= n - 1; i++){ printf("%d ",arr[i]); } printf("\n-------------------------------\n"); printf("This program is posted at learnnc.com"); return 0; }
Output:
Examples of arrays in C / C++
Here, we have two examples with array
in C/C++. These are basic examples when using array
in C/C++.
Example 1: Displaying elements even numbers in arrays in C / C++
C++ programming:
#include <iostream> using namespace std; int main() { int n; do{ cout<<"Enter the size of the array: "; cin>>n; if(n <= 0) cout<<"Please enter the size of the array greater than 0 !!!\n"; }while(n <= 0); int arr[n]; for(int i = 0; i <= n - 1; i++){ cout<<"Enter the element "<<"[" <<i<<"]: "; cin>>arr[i]; } cout<<"Elements in array is: "; for(int i = 0; i <= n - 1; i++){ cout<<arr[i]<<" "; } cout<<"\nEven numbers in array: "; for(int i=0; i<n; i++){ if(arr[i] % 2 == 0) cout<<arr[i]<<" "; } cout<<"\n-------------------------------\n"; cout<<"This program is posted at learnnc.com"; return 0; }
C programming:
#include <stdio.h> int main(void) { int n; do{ printf("Enter the size of the array: "); scanf("%d", &n); if(n <= 0) printf("Please enter the size of the array greater than 0 !!!\n"); }while(n <= 0); int arr[n]; for(int i = 0; i <= n - 1; i++){ printf("Enter the element [%d]: ",i); scanf("%d", &arr[i]); } printf("Elements in array is: "); for(int i = 0; i <= n - 1; i++){ printf("%d ",arr[i]); } printf("\nEven numbers in array: "); for(int i=0; i<n; i++){ if(arr[i] % 2 == 0) printf("%d ",arr[i]); } printf("\n-------------------------------\n"); printf("This program is posted at learnnc.com"); return 0; }
Output:
Example 2: Find the sum of elements in array in C / C++
C++ programming:
#include <iostream> using namespace std; int main() { int n, sum = 0; do{ cout<<"Enter the size of the array: "; cin>>n; if(n <= 0) cout<<"Please enter the size of the array greater than 0 !!!\n"; }while(n <= 0); int arr[n]; for(int i = 0; i <= n - 1; i++){ cout<<"Enter the element "<<"[" <<i<<"]: "; cin>>arr[i]; } cout<<"Elements in array is: "; for(int i = 0; i <= n - 1; i++){ cout<<arr[i]<<" "; } for(int i=0; i<n; i++){ sum += arr[i]; } cout<<"\nSum of elements in array: "<<sum; cout<<"\n-------------------------------\n"; cout<<"This program is posted at learnnc.com"; return 0; }
C programming:
#include <stdio.h> int main(void) { int n, sum = 0; do{ printf("Enter the size of the array: "); scanf("%d", &n); if(n <= 0) printf("Please enter the size of the array greater than 0 !!!\n"); }while(n <= 0); int arr[n]; for(int i = 0; i <= n - 1; i++){ printf("Enter the element [%d]: ",i); scanf("%d", &arr[i]); } printf("Elements in array is: "); for(int i = 0; i <= n - 1; i++){ printf("%d ",arr[i]); } for(int i=0; i<n; i++){ sum += arr[i]; } printf("\nSum of elements in array: %d",sum); printf("\n-------------------------------\n"); printf("This program is posted at learnnc.com"); return 0; }
Output:
Above are two basic examples when using array
in C / C++. You can check out more examples here.