C One Dimensional Array

In this lesson, you will learn about Array in C, declaring arrays, and manipulating arrays, along with examples to better understand the topic.

What is an Array?

An array stores multiple values in one variable; it can retain more than one value at a time. An array in C is an ordered map. A map is a sort associating values with keys such as Array, list (vector), a hash table (a map implementation), dictionary, collection, stack, queue, and probably more.

If you have a list of products (for instance, a list of fruits), it might look like this to store each fruit in a variable:

Fruit1 = "Apple";
Fruit2 = "Banana";
Fruit3 = "Mango";
Fruit4 = "WaterMelon";
Fruit5 = "Dates";

What if your program requires you to loop through the list of fruits and discover a particular one? And what if you have 300 fruits to define? Creating an array is the answer. An array can hold multiple values under a single name, and you can access the values by referring to an index number.

Why do we need Array?

Create an Array

You can create an array using the datatype arrayname[sizeofarray]

Basic Syntex of Array

DataType arrayName[Sizeofarray];

For example:

int marksOfSubject [5];

In the example above, the Array named marksOfSubject is of int type, and its size is 5. It means marksOfSubject can have five integer types of values.

Initialize an Array

You can initialize a marksOfSubject array like this.

BasicSyntex of initializing an Array

DataType arrayName[Sizeofarray]= {value1,value2,value3,value4,value5}

Example

int marksOfSubject [5]= {75, 100, 90, 80,60};

Access an Array

See in the table below marksOfSubject Array is of size 5 and if you want to access its element, it will be accessed through the first index by writing syntax marksOfSubject [0] second by marksOfSubject [1], and so on.

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Example of Array in C

// Example of array
#include <stdio.h>
int main ()
{
//Defining an array marksOfSubject of int type and size of 5 elements
  int marksOfSubject[5] = { 75, 100, 90, 80, 60 };
  printf ("Printing the elements from 1 to 5 \n");
  printf ("%d\n", marksOfSubject[0]);
  printf ("%d\n", marksOfSubject[1]);
  printf ("%d\n", marksOfSubject[2]);
  printf ("%d\n", marksOfSubject[3]);
  printf ("%d\n", marksOfSubject[4]);
  return 0;
}

Output

Printing the elements from 1 to 5 
75
100
90
80
60

Example of an Array using for Loop

// Example of array
#include <stdio.h>
int main ()
{
  int marksOfSubject[5] = { 75, 100, 90, 80, 60 };
  printf ("Printing marksOfSubject elements\n");
// Loop will print all the marksOfSubject stored
  for (int var = 0; var < 5; ++var)
    {
      printf ("%d\n", marksOfSubject[var]);
    }
  return 0;
}

Output

Printing marksOfSubject elements
75
100
90
80
60

 Example of Array taking input and displaying output

// Example of array
#include <stdio.h>
int main ()
{
  int marksOfSubject[5];
  printf ("Please enter marks of 5 subjects \n");
// Loop will execute 5 times and takes inputs
  for (int var = 0; var < 5; ++var)
    {
      scanf ("%d", &marksOfSubject[var]);	// storing the input value in an array
    }
  printf ("Printing marksOfSubject elements\n");
// Loop will print all the marksOfSubject stored in above array one by one
  for (int var = 0; var < 5; ++var)
    {
      printf ("%d\n", marksOfSubject[var]);	// accessing the array elements
    }
  return 0;
}

Output

Please enter marks of 5 subjects 
8
9
4
1
7
Printing marksOfSubject elements
8
9
4
1
7

Access element out of its bound

Let’s say we have an array of size 5 and you want to access the array elements from that array index 0 to 4. The program will execute correctly. But if you want to access an index 5 that doesn’t exist in memory, then an unexpected behavior will be thrown.

To understand this concept, see the below example. It shows a strange value.

// Example of array out of bound
#include <stdio.h>
int main ()
{
  int marksOfSubject[5] = { 75, 100, 90, 80, 60 };
  printf ("Accessing the elements from 1 to 6 \n");
  printf ("%d\n", marksOfSubject[0]);
  printf ("%d\n", marksOfSubject[1]);
  printf ("%d\n", marksOfSubject[2]);
  printf ("%d\n", marksOfSubject[3]);
  printf ("%d\n", marksOfSubject[4]);
  printf ("%d\n", marksOfSubject[5]);	// accessing the index out of bound
  return 0;
}

Output

Accessing the elements from 1 to 6 
75
100
90
80
60
32766

Notice the 6th element has a random value that doesn’t not below the array.

In this lesson, you learned about one-dimensional arrays. In the next lesson, you will learn about two-dimensional arrays and their usage.